BS 9999 Handbook - Effective Fire Safety in the Design, Management and Use of Buildings

The BS 9999 Handbook

Effective fire safety in the design, managementand use of buildings

Michael Green and Jonathan Joinson

First published in the UK in 2010

by

BSI

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© British Standards Institution 2010

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British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

ISBN 978-0-580-67508-9

Introduction

BS 9999 and consequently this guide are intended for use by designers, fireengineers, fire and rescue services and fire safety managers. However, they arealso clearly of value to regulators, enforcers, operators/end users/clients, insurersand contractors. The standard is designed as a holistic guide to bring togetherthe key areas of fire safety:

• design for means of warning and escape;• fire resistance performance to protect means of escape and provide structural

stability;• the provision of access and facilities for fire fighting;• fire safety management.

BS 9999 contains a number of important changes from the guidance in theBS 5588 series, particularly in the approach for design of means of escape andconstruction. It also introduces the concept of the risk profile. It brings forwardguidance from BS 5588-5 and BS 5588-12 and has taken into account the inputfrom a major public consultation process. When compared with the variousnational guidance documents and other British Standards, some fire protectionmeasures have been increased and others have been reduced to better reflectthe risks that are more clearly identified by relating to both the characteristicsof occupants and the potential for fire development in a more integrated way.This applies to means of escape, fire resistance and fire-fighting provisions.The recommendations specifically relating to fire-fighting have been updatedto take into account the findings of the Building Disaster Assessment group(www.communities.gov.uk/fire/researchandstatistics/fireresearch/buildingdisasterassessment/).

In the UK, technical guidance on fire safety is provided at three different levels.This permits a design approach to be adopted that corresponds to the complexityof the building and to the degree of flexibility required. The three levels are asfollows.

• General approach. This level is applicable to a majority of building workundertaken within the UK. Fire precautions designed into the buildingusually follow the guidance in various national prescriptive documents(e.g. Approved Document B) published to support legislative requirements.

The BS 9999 Handbook xvii

• Advanced approach. This is the level for which BS 9999 is provided.Guidance provided gives a more transparent and flexible approach throughuse of a structured process to risk-based design to account for different fireand human factors. Much of the guidance in BS 9999 is based on fire safetyengineering principles, although it is not intended as a guide to fire safetyengineering.

• Fire safety engineering. This is the level for which BS 7974 is provided. Thislevel provides an alternative approach to fire safety and can be the onlypractical way to achieve a satisfactory standard of fire safety in some largeand complex buildings.

An early decision by the client and the design team on the most effective andefficient approach is recommended so that the needs of the project are bestserved. There might be circumstances in which it is necessary to use onepublication to supplement another, but care needs to be taken when using a‘pick-and-mix’ approach as it is essential to ensure that an integrated approachis used in any one building. Clear justification is necessary if this approach isadopted.

The method of procurement of a building and the time at which a futureoperator/end user can be identified is subject to a number of variables thatcannot easily be prescribed. It is therefore particularly important that fire safetyinformation, risk assessments and other relevant data throughout the wholedesign, procurement and the operation of a building are made available bythose responsible at the different stages.

As per the standard, this guide does not cover the design of individual dwellinghouses, flats or maisonettes. For guidance on the fire safety design of thesetypes of premises refer to BS 5588-1.1

Use of this handbook

This handbook, like BS 9999, takes the form of guidance and recommendations.It should not be quoted as if it were a specification, and particular care shouldbe taken to ensure that claims of compliance are not misleading.

xviii The BS 9999 Handbook

Introduction

1BS 5588-1 is due to be replaced by BS 9991 in late 2010.

The primary purpose of this handbook is to provide a ‘pocket’ guide to the useof BS 9999 that is easy to use and draws together the key areas of fire safetydesign that require consideration during the early development of designconcepts. The handbook provides an aid to the understanding and use ofBS 9999 and is not intended to be a substitute for the standard. The mostcommonly used data, tables, figures and a ‘Key Points’ list at the beginning ofeach chapter provide a quick and effective overview of the measures that maybe necessary. In addition, a methodology is presented to help the user find thebest approach to deploy the flexible design recommendations introduced byBS 9999.

Although it is a prescriptive guide, BS 9999 has a relationship with fire safetyengineering, and the opportunity for adopting such an approach has beenidentified in a number of places throughout this handbook. The use of theguidance involves limited calculation and engineering but does requireknowledge of fire safety in order to best judge the most appropriate packageof fire protection measures, management and training. It does allow for thetrade-off of one fire protection measure against another within a limitedframework beyond which a fire safety engineering approach would be required.

The BS 9999 Handbook xix

Introduction

Contents

List of tables xi

List of figures xiii

Foreword xv

Introduction xvii

1. General 1Principles 1

Spread of fire and smoke 2

The impact of fire on people 3

Historic buildings 4

Property and business continuity protection 5

Means of escape for disabled people 6

The full circle of fire safety 7

2. The concept of a risk profile 10Key points 10

Background 10

Occupancy characteristics 11

Fire growth rate 12

The value of sprinklers within BS 9999 16

3. Methodology and tactics for use of the standard 17Key points 17

Background 17

Inclusion of automatic sprinklers 20

Inclusion of automatic fire detection and alarm 20

Taking advantage of high ceilings 21

Example of the application of the allowable variations and the

associated benefits 21

Multi-space buildings with various risk profiles 23

The BS 9999 Handbook vii

4. Allocation of fire protection measures 24Key points 24

Background 24

Additional fire protection measures 27

5. Managing fire safety – design, occupation and construction 28Key points 28

Background 28

Management levels 29

Designing so that a building can be managed 30

Fire safety manual 34

6. Design for means of escape 38Key points 38

Background 38

Additional fire protection measures 43

Effect of automatic fire detection 44

Effect of ceiling heights 45

Maximum acceptable variations 46

Travel distance 46

Door and escape stair widths 47

Floor space factors 48

Alternative escape routes 48

Inner rooms 52

Dead-end corridors 54

Progressive horizontal evacuation 54

Escape for disabled people 55

External protection to escape stairs 58

7. Access and facilities for fire-fighting 59Key points 59

Background 60

Risk profiles and fire-fighting provisions 60

viii The BS 9999 Handbook

Contents

Smoke control for fire-fighting shafts 66

Smoke venting from basement floors 66

Smoke venting from car parks, loading bays and service roads 67

8. Designing the building structure 68Key points 68

Background 68

Compartmentation 82

Openings within fire-resisting construction (compartmentation or

escape routes) 83

External fire spread between neighbouring buildings 84

9. Recommendations for atria 90Key points 90

Background 91

Escape routes 92

Smoke and heat control systems 97

10. Recommendations for theatres, cinemas and similar venues 98Key points 98

Background 99

Seating and exit layouts 99

Furnishings, fabrics and decorative features 100

Stage areas 101

11. Recommendations for shopping complexes 102Key points 102

Background 103

Means of escape and motivation to escape 104

Smoke control 104

Fire protection 104

Uncovered shopping complexes 105

Small shopping developments or arcades 105

Covering existing streets 105

The BS 9999 Handbook ix

Contents

12. Process plant and outdoor structures 106

Key points 106

Background 106

13. Worked example – two storey retail unit 109

14. Worked example – high-rise office building 114

15. Worked example – mixed-risk profile building 119

Bibliography 128

x The BS 9999 Handbook

Contents

1. General

Principles

The recommendations given in the British Standard are general, and all fireprotection measures, procedures, etc., need to take into account the particularcircumstances of the individual building or complex concerned. The samerecommendations generally apply to both existing and new buildings, butexisting buildings, especially historic buildings, often pose problems that areunlikely to arise in new buildings and, therefore, require further consideration byadopting a flexible approach in the risk assessment process.

Although it is a prescriptive guide, BS 9999 provides a higher level of flexibilitythan many prescriptive standards. It supports the concept of achieving the bestbalance between an adequate performance and reasonable value. This has beenpossible because the original basis of the recommendations gave recognition tomany of the engineering principles embodied in BS 7974. Where relevant anduseful, a brief background is provided in each of the chapters.

The guidance is straightforward to use for routine and typical buildings, but theinbuilt flexibility will also support a sustainable reuse of our built environment.The following areas are an essential contribution:

• The identification of alternative flexible solutions to support the preservationand the extended use of historic buildings, balancing the requirements ofmodern construction standards and the need to be sensitive with historicstructures and finishes, is required.

• The logical approach that is embodied in the code enables a relatively simplerisk assessment to appraise a change of use by addressing the fundamentalsthat affect the outcomes: the fire load and the occupancy characteristics.This will increase the overall ability of the design community to identifyalternative solutions that are good value, sustainable and safe.

• The design of a new building to be adaptable for reuse at some future timeis a new challenge, which if successful will significantly enhance the life ofour building stock. The flexibility contained within BS 9999 allows designersto plan for alternative future uses without the addition of a disproportionatecost premium. The same flexibility equally allows alternative interpretationswhen appraising an existing building for alternative uses.

The BS 9999 Handbook 1

No one building or operator/end user/client is exactly the same as another, soa code of practice, such as BS 9999, can provide only a framework for thedesigner and the operator/end user/client to make an informed judgement onthe most appropriate package of fire protection measures to meet both therequirements of the designer and the objectives of the building operator/enduser/client. Fire precautions in all premises, however old, need to be seen as awhole, a package aimed at achieving an acceptable standard of fire safety.

BS 9999 applies straightforwardly where premises have a single main use andare contained in a single, separate building. However, complications might arisewhere a building comprises two or more different main uses. In such cases, it isimportant to consider the effect of one risk on another. A fire in a shop orunattended office could have serious consequences on, for example, a residentialor hotel use in the same building. Similarly, a high fire risk in one part of abuilding could seriously affect other areas in another part of that building. Aworked example in Chapter 15 provides an illustration of how to approachdifferent risk profiles within a single building.

Spread of fire and smoke

A common basis for designing fire safety measures lies in the identification ofthe possible causes and sources of fire, and the evaluation of the developmentand spread through a building.

The fact that outbreak of fire is more likely to occur in furnishings, decorations,finished goods, raw materials, chemicals, equipment, electrical services, processplant, or service plant in a building has been taken into account in the developmentof the standard. Initially, a fire creates a hazard only in the part of the buildingin which it starts, and it is unlikely to involve a large area in the first instance,although it can subsequently spread to other parts of the building, and verticalshafts such as lifts and service risers are a particular risk. Fire is less likely tospread if passages, corridors, lobbies or stairways, intended for access or meansof escape, are kept clear of combustible materials. As the fire grows, flamesincrease in height, reach the ceiling and are deflected horizontally, radiatingheat downwards and accelerating fire growth. If the ceiling is combustible, itcan ignite and add to the volume of flame and speed of fire growth. If thespace has insufficient openings to provide a continuing air supply, the burningrate diminishes as it draws on increasingly vitiated air, but the gases generatedare then extremely toxic.

2 The BS 9999 Handbook

General

The impact of fire on people

A fire occurring anywhere within a compartment of a building has to be regardedas presenting a hazard to all occupants within that compartment, even thoughthe hazard may seem small in the initial stages. When a fire occurs in anenclosed space, hot smoke-laden toxic gases rise to form a layer, which at firsthas a tendency to flow under the ceiling and then deepens to fill the wholespace. Smoke is likely to be the first sign that there is a fire. For higher andlarger spaces, it takes longer for the space to fill with smoke, and so there ismore time for escape, and therefore longer travel distances and smaller stairsare possible. Higher fire growth rates reduce the time available.

When smoke descends down to head height it causes difficulty in breathing andimpairs visibility, which interferes with the efforts of occupants to find their waytowards the exits. Smoke can cause intoxication, disorientation, incapacity,unconsciousness and, in the worst-case scenario, fatalities.

These considerations are particularly important when dealing with largenumbers of people, who might be unfamiliar with their surroundings, and varywidely in age and degree of mobility. Also, when people are unfamiliar withtheir surroundings they might initially go in the wrong direction or they mightnot take the most direct path and, therefore, the average speed of travel to anexit could be slower than a typical average walking speed.

To facilitate escape it is therefore necessary:

• to ensure that protected escape routes are provided and that they areadequately safeguarded against the ingress of smoke;

• to limit the time people have to travel before they reach a protected route orfinal exit;

• to consider reverse flows that might occur as a result of a particular exitroute being unavailable;

• to plan evacuation for disabled people in an integrated manner.

A means of smoke ventilation might be necessary to assist the fire and rescueservice and, if operated automatically, can also assist escape from the building.

After the outbreak of fire there might only be a short time during which theactions necessary for ensuring the safety of occupants can be carried out. Thistime will be sufficient only if all provisions for the safety of people from fire areplanned and managed so as to be effective when the occasion arises.


General

Historic buildings

Many historic buildings are listed, and permitted alterations are limitedwithout the agreement of the appropriate authorities. The advice of consultativebodies, such as English Heritage, should be sought in the early stages of design.The appropriate authorities sometimes agree to limited modifications toimprove life safety where, in turn, there will be added long-term protectionand preservation of the original building fabric. Issues relating to historicbuildings include:

• the preservation of the ambience and important features of the building,such as timber linings to accommodation stairs and slender cast ironstructure, both of which can sometimes conflict with the desired fire safetybut can be accommodated with suitable compensating features;

• the existing construction of the building, including hidden features such ascavities through which fire could spread and the fire performance of walls,partitions and floors;

• the interrelationship between life safety and measures to protectproperty/contents;

• the fire performance of the building structure. Although modernconstruction standards seldom apply to historic buildings, action to improvethe level of fire and life safety might be necessary on the basis of change ofuse or due to the need to reduce the fire risk and potential for loss of thebuilding and its contents.

In assessing the fire safety management needs of an existing building that isbeing modified, it is essential to have a full understanding of the existingstructure (Appraisal of Existing Structures, 3rd edition, IStructE) and any firesafety provisions incorporated. Any change in use of the premises that couldaffect the fire risk profile (e.g. increased fire load and process risks, introducingthe public, changes to sleeping risk, seasonal changes) should be considered.Also the legislation and guidance introduced since the premises were originallyconstructed or last altered, or since their fire safety was last assessed, should bereviewed.

In both new construction and upgrading existing buildings, the fire precautionsare interrelated and weaknesses in some areas can be compensated for bystrengths in others. BS 9999 provides a level of flexibility that allows the fireprotection measures and the risks to be assessed to enable reasonable practicalsolutions to be designed.


General

Property and business continuity protection

The guidance and recommendations in BS 9999 are primarily concerned withthe protection of life. The provision of fire safety systems for life safety does notnecessarily give adequate protection to property or to the continuity of thebusiness carried out in the building.

Smoke and fire spread are major causes of property damage and losses thatinclude:

• property: contents, fabric and building services;• business: loss of trade, loss of operational continuity, loss of records.

The objectives are first to reduce the chance of fire starting and second in theevent of fire starting to reduce the consequences of that fire. Because manyof the features necessary for life safety are common, the risk assessment forproperty and business continuity protection could be an extension to other riskassessments carried out for life safety. The following are the primary means ofachieving the objectives:

• the first barrier to property and business loss is the level of fire preventionmanagement in the building. This is to ensure that ignition hazards areeliminated or controlled, that operations in the building are carried outappropriately and that combustible loads are subject to control and goodhousekeeping.

• smoke management (mechanical, natural, pressurization) to prevent damagefrom heat and corrosive chemicals in the smoke;

• compartmentation and structural fire protection to reduce spread of firebetween spaces. The complete involvement of the whole fire compartment isan extreme-event scenario. Adequate detailing of cavity barriers, fire-stoppingdoors, shutters, fire resistance, etc. is important to maintain the performanceof the compartment walls and floors.

• fire-fighting facilities, including consideration of speed of response and thetactics for external and internal fire-fighting;

• external fire spread and building separation. For most buildings it is expectedthat these provisions for life safety will also be adequate for propertyprotection. However, for some buildings and uses the provision may need tobe more stringent. Consideration should be given to buildings having highlyglazed façades.

• automatic suppression systems to reduce fire severity such as sprinklers, etc.


General

The consequences of fire on property and business loss can be highlighted tothe owner, occupier, operator/end user/client, tenant, designers and insurersand can involve discussions on the acceptable level of risk.

Any changes in the design added for the purpose of property protection shouldbe discussed with the relevant authorities to ensure that there is no adverseimpact on life safety. If a conflict exists between the provisions for life safetyand property protection that cannot be resolved, then life safety takes priority.

The risk assessment could range from a simple statement outlining the potentialproperty and business losses that are acceptable to business managers and theirinsurers, through to a rigorous quantified analysis of probabilities andconsequences of fire. Whatever method is used, the aims of the risk assessmentshould be understood by all concerned.

The insurance industry has produced various guides that are directed at propertyprotection (including FPA guide Essential Principles and guidance published bythe Arson Control Forum, Arson Prevention Bureau and Zurich Municipal). Arsonand vandalism are addressed by guidance produced by the Arson Control Forumand the Arson Prevention Bureau.

Many insurers use the LPC Design Guide for the Fire Protection of Buildings as abasis for providing guidance to the building designer on what they require.

BS 9999 is the first significant design standard that embeds the quality of themanagement into the design process. Many fire losses are due wholly or in partto failures in management so it makes good sense to draw attention to themanagement needs. It will also be increasingly important for the insuranceindustry to build the quality of the management into their methodology to helpreduce losses. However, trade-off for enhanced management, enabling reductionsin the built provision, is not allowed in the standard.

Reference should be made to Annex A of BS 9999 for additional considerationsfor property and business continuity protection.

Means of escape for disabled people

Means of escape for disabled people, and the associated fire safety strategy,should be considered as an integral part of the design process, and not as aseparate issue. Where a building is designed and managed inclusively to provide


General

access for all users, the facilities provided should, where appropriate, be used toimprove egress arrangements.

Fire safety for disabled people is included within the standard; this includesconsideration of all disabilities and is not restricted to guidance for assistingwheelchair users. Specific guidance on means of escape for disabled people isgiven in BS 9999: Clauses 17.7 and 18.8; general guidance on fire safetyprocedures for people at particular risk is given in BS 9999: Clause 44.3; andmeasures to aid the evacuation of disabled people are described in BS 9999:Clause 46.

Disabled people can be at particular risk in the event of a fire and need appropriateprotection facilities. These might include relevant provisions for those requiringassistance, such as:

• appropriate means for giving warning in the event of fire;• management planning;• appropriate fire instructions in alternative formats;• appropriate wayfinding systems;• evacuation lifts or protected refuge areas and devices for taking people down

or up stairs.

Special management procedures might be required when it is reasonablyforeseeable that the proportion of disabled users in a building will be relativelyhigh or where the use of the premises is likely to result in groups of wheelchairusers being present (e.g. some types of sporting, entertainment, transport orpublic assembly building).

The full circle of fire safety

The concept of the full circle of fire safety is inherent within a comprehensivewhole-life approach to fire safety. However BS 9999 is exceptional in that itincorporates an explicit connection between the use, the design and the operation.Historically, the management for fire safety has not been a significant part ofthe design process, and this is currently still the case in many countries.

The full circle of fire safety requires effective connectivity between the clientbrief, design, operational fire strategy and ultimately whether the actualoperational approach meets with the client intentions and the full circle.


General

8The

BS9999

Handbook

Gen

eral

Operationalfire safety plan

Firestrategy

Design aspirations

Client briefand policy

and objectives

Fire risk management

Qualitative design review

Acceptance criteria

Zone models

Risk assessmentDefine management standard

Staff training

Design products

Procure fire systems

Structural fire design

CFDEvacuation modelling

Commissioning and testing

Maintenance

Operational requirements

Fire safety plan Fire testsRisk assessments

Review fire safety plan

Auditing and reporting

Cause and effects

Operational certification

Building regulations approval

Fire-fighting

Science

Figure 1 – Circle of fire safety

© Buro Happold

It is likely that simple buildings complying with the recommendations of thestandard will only necessitate consideration of a selection of the sub-componentsof the circle of fire safety. However, complex buildings, particularly where a fireengineering approach is adopted, will probably necessitate the adoption of themajority of sub-components identified in Figure 1.


General

2. The concept of a risk profile

Key points

• The risk profile associated with a space is a combination of the ‘occupantcharacteristics’ and the ‘fire growth rate’ and is the principal driver for thedevelopment of the fire safety design and provision of a suitable packageof fire safety measures within BS 9999.

• The ‘occupancy characteristic’ (Table 1) embodies the familiarity ofoccupants with their surroundings, their alertness, their response to fireand warning and hence the time taken to evacuate to a place of safety.

• The ‘fire growth rate’ (Table 2) embodies the growth and scale of a fireand hence the time available for those occupants to evacuate and theseverity of the fire impacting on the structure. The addition of sprinklersimproves safety and thus reduces the ‘fire growth rate’, which alters therisk profile for the space.

• There are certain combinations of ‘occupant characteristics’ and ‘firegrowth rate’ that are not allowable and outside the scope of the guidancewithin BS 9999. Risk profiles A4, B4 and C4 will require the addition offire suppression/sprinklers or the adoption of a fire engineered approach.

Background

There are two fundamental inputs to the design of a building that drive thespecification of the fire protection measures and the approach to fire safetymanagement. Every other input is a decision made by the designer, anoperator/end user/client, or the approving authorities. The two inputs areassociated with the intended use and are as follows:

1. The ‘occupancy characteristics’. The principal variables are whether themajority of occupants are familiar with the building or whether there is asleeping use. Occupant characteristics will also influence the approach todesign for disabled people.

2. ‘The ‘fire growth rate’. This is derived from the use and management of thebuilding, and encompasses:a. the growth rate of a fire, which is a key factor in the means of escape;


b. the severity of the fire that affects the performance of the structure,construction and the compartmentation.

By a combination of the above two inputs the ‘risk profile’ for the building orspace is defined.

Occupancy characteristics

The occupancy characteristics for a single use are usually fairly clear and can bedetermined from Table 1. Complications can arise when there is a mix of uses.


The concept of a risk profile

Occupancycharacteristic

Description Examples

A Occupants who are awake andfamiliar with the building

Office and industrial premises

B Occupants who are awake andunfamiliar with the building

Shops, exhibitions, museums,leisure centres, other assemblybuildings etc.

C Occupants who are likely to beasleep:

Ci • Long-term individualoccupancy

Individual flats without24-hour maintenance andmanagement control on site

Cii • Long-term managedoccupancy

Serviced flats, halls ofresidence, sleeping areas orboarding schools

Ciii • Short-term occupancy Hotels

DA) Occupants receiving medicalcare

Hospitals, residential carefacilitiesB)

EC) Occupants in transit Railway stations, airports

A) Currently, occupancy characteristic D, medical care, is dealt with in otherdocumentation and is outside the scope of this British Standard.B) Under some circumstances, residential care facilities may be classified as occupancycharacteristic Cii.C) This occupancy characteristic is included for completeness within this table but isnot referred to elsewhere in this British Standard.

Table 1 – Occupancy characteristics

Unless the uses can be clearly delineated, it is advisable to adopt the higherrequirement. A worked example is provided in Chapter 15 where a number ofdifferent risk profiles are contained within the same building.

Fire growth rate

The fire growth rate as defined by BS 9999 embodies both of the following:

• the rate of fire growth, which is of primary concern for means of escape,travel distance, doors stairs, etc.;

• fire load and ventilation and thus the severity of the fire impacting on thestructure.

Table 2 provides a simple summary of the typical fire loads with the associatedfire growth rate.

The selection of the fire growth rate requires some thought and consideration.For example an office fire growth rate could vary between 1 and 3, although 3would be unlikely unless there are very significant amounts of open storageareas. A fire growth rate of 1 is possible as offices become paperless, although itmay be unwise to select 1 for the design of a new facility as this may reducefuture flexibility, unless the client is able to prescribe with some certainty intothe future or in the case of temporary use. Another example for consideration isthat of a shop. Some boutique-style shops with products that are well spacedand presented for sale in low densities may have a fire growth rate of 1, but



Fire growthrate

Examples Fire growthparameterA)

kJ/s3

Slow Banking hall, limited combustible materials 0.0029

Medium Stacked cardboard boxes, wooden pallets 0.012

Fast Baled thermoplastic chips, stacked plasticproducts, baled clothing

0.047

Ultra-fast Flammable liquids, expanded cellular plasticsand foam

0.188

A) This is discussed in PD 7974-1.

Table 2 – Fire growth rate

conversely a shop with head-height shelving may be growth rate 3, or possibly4, if there are significant volumes of combustible materials. However, a firegrowth rate 3 is considered as typical within the standard as it covers a broadrange of shops, but as highlighted above will not apply to every type of shop.The designer in consultation with the client does need to make a well-judgeddecision that reflects the intended use. Table 2 gives some typical values that areuseful for initial guidance, but each case should be specifically assessed on itsown merits.

Table 3 highlights how risk profiles are defined, and risk profiles for typical areaswithin a building are given in Table 4.

As this standard derives from a very simple logic, it enables a more flexibleresponsive approach compared with traditional prescriptive guidance. Thishandbook includes a description of how this flexibility can best be deployed.The risk profile provides a simple and very effective basis for handling andassessing the variations in risk, the related package of fire protection measuresand the need for management.



Occupancy characteristic(from Table 2)

Fire growth rate Risk profile

A

(Occupants who are awake and familiarwith the building)

1 Slow A1

2 Medium A2

3 Fast A3

4 Ultra-fast A4

B

(Occupants who are awake andunfamiliar with the building)

1 Slow B1

2 Medium B2

3 Fast B3

4 Ultra-fast B4

C

(Occupants who are likely to be asleep)

1 Slow C1

2 Medium C2

3 Fast C3

4 Ultra-fast C4

Table 3 – Risk profile (BS 9999: Table 4)



Occupancy Riskprofile


Administration office A2 Gymnasium/leisure centre B2

Amusement arcade B2 Indoor games/training roomsin schools

B2

Archive/library reading area B3 Kitchen A3

Art gallery B1/B2 Licensed betting office (publicarea)

B1

Assembly hall B2 Lobbies B1

Banking hall B1 Lounge (other than dwelling) B2

Bar B2 Machine/printing room A3

Bazaar B2/B3 Mechanical plant room A4

Bedroom/study bedroom Cii2 Meeting room B2

Bed-sitting room Cii2 Museum B2

Billiards or snooker room B2 Office (closed-plan or officeless than 60 m2)

B2

Bingo hall B2 Office (open-plan exceeding60 m2)

A2

Bowling alley B2 Reading room B2

Business centre B2 Reception area B1

Canteen A2 Restaurant B2

Classroom A2 Shop sales area B3

Club B2 Showrooms B3

Committee room A2 Skating rink B1

Common room A2 Stadia and grandstands B1

Computer room B2 Staffroom A2

Concourse or shopping mall B2 Storage and warehousing A2/A3/A4

Conference room B2 Studio (radio, television, film,recording), non-public

A2

Crush hall B2 Studio (radio, television, film,recording), public

B2

Table 4 – Examples of risk profiles (BS 9999: Table 5)

The risk profile concept is a common thread throughout BS 9999, althoughthere are some areas where reference to a ‘purpose group’ remains to enableeffective cross-reference to other guidance documents. Where guidance withinBS 9999 refers to ‘assembly and recreation’, ‘shops’ and ‘factories’, these areknown as ‘purpose groups’ as defined within Table D1 of Approved DocumentB. The designer should reference this document to determine which purposegroup their occupancy falls within. By using responsible judgement, it may bepossible to map a risk profile to a purpose group where they continue to bereferenced, although this is currently beyond the scope of the standard.

Risk profile assessments are carried out on a case-by-case basis, as highlighted inthe examples considered above. Because of the relatively high risks, ultra-fastfires are deemed to be unacceptable and therefore risk profiles A4, B4 and C4are not allowable unless an effective localized suppression system or automaticsprinklers are added to alter the risk profiles to A3, B3 and C3 respectively. Inaddition, risk profile C3 may also be unacceptable under many circumstancesunless special precautions are taken. Fire safety engineering can offer analternative approach to those risk profiles that are not allowable within BS 9999.





Dance area B2 Teaching laboratories A3

Deposit/strongroom A2/A3 Theatre/cinema/concert hallauditoria

B2

Design studio/drafting office A2 Theatre stages A2/A3

Dining room B1 Trading floor B2

Dormitory Cii2 Trading gallery B2

Exhibition areas B2/B3 Venue for pop concerts B1

Factory production area A2/A3 Waiting area/visitors lounge B1

Filing room/store A3 Waiting room B1

Foyers B1 Workshop A3

Table 4 – Examples of risk profiles (BS 9999: Table 5)(contd)

Occupancy characteristic ‘C’ is divided into the following sub-categories:

• Ci – long-term individual occupancy, i.e. individual flats without 24-hourmaintenance and management control on site;

• Cii – Long-term managed occupancy, i.e. serviced flats, halls of residence,sleeping areas or boarding schools.

• Ciii – Short-term occupancy, i.e. hotels.

The value of sprinklers within BS 9999

Sprinklers help to improve performance in a variety ways of including the safetyof people, performance of the construction as well as reducing the overallrisks of spread of fire and the consequent protection of property and businesssustainability. In particular, consideration should be given to the following whenconsidering the value of sprinklers in a particular case.

• A person in the space where the fire originates may be safer, as the presenceof sprinklers limits fire growth and reduces temperature as well as smokeproduction. At best sprinklers put a fire out, but they may only slow the firegrowth rate if the circumstances for extinguishing the fire are not ideal.BS 9999 conservatively assumes a reduction in growth rate by allowing areduction of one step in the fire growth rate (i.e. 2 to 1, 4 to 3, etc.).

• Sprinklers may also reduce the chance of fire spreading from one room toanother.

• The chance of a fire seriously affecting the fire performance of a structurereduces if sprinklers are present, and therefore a lower fire resistancerequirement is reasonable to achieve a given performance.

• For the same reasons as for the structure, the chances of fire spread betweenbuildings is beneficially reduced.

Automatic sprinkler systems should be designed and installed in accordancewith BS EN 12845 (new systems) or BS 5306-2 (existing systems). Where it isproposed to modify the risk profile by using a fire suppression system other thana traditional water-fed sprinkler system, it will need to be demonstrated that thissystem achieves the equivalent standard of fire protection and reliability.

The list of example risk profiles in Table 4 is not exhaustive and should not beprescriptively applied without due consideration. As highlighted previously, it ispossible for office spaces to have risk profiles varying from A1 to A3.



3. Methodology and tactics for use of thestandard

Key points

• Before beginning the design of a building in accordance with BS 9999, itis essential that knowledge of any fire protection systems due to client orinsurance requirements is established.

• Figure 2 outlines a process for approaching the interaction between riskprofile and the related fire protection measures to ensure that the designdoes not fall short of the recommendations within the standard.

• The provision of automatic sprinklers within a space will improve safetyand enable a change in the risk profile, which then affects all relatedrecommendations, so an early decision on this helps the process greatly.

• The provision of automatic detection and alarm and/or high ceilings canallow increased travel distances and reduced escape route widths.

• Chapter 15 provides a worked example that highlights how therecommendations of BS 9999 can be applied to a building containingmultiple-risk profiles.

Background

The guidance provided within BS 9999 is flexible and allows trade-off among therisk profile, sprinklers and the package of fire protection measures. For exampleautomatic sprinklers will result in a change to the risk profile (e.g. B3 to B2 whensprinklers are introduced into a shop), and high ceilings or automatic detectionand alarm can directly allow increased travel distances and reduced escape routewidths. Therefore, use of the standard can provide a high level of flexibility for newbuildings and renewed flexibility for the refurbishment of existing building stock.

Variation in BS 9999 design recommendations, responding to risk profile andthe inclusion of fire protection measures within a room or space, relate primarilyto the following:

• design of means of escape (refer to Chapter 6);• fire resistance period(s) of a building (refer to Chapter 8);• compartment limitations.


Design recommendations in other areas of fire safety design within BS 9999 donot vary in response to the inclusion of additional fire protection measures. Notethat the variation of design recommendations can be applied only within roomsor spaces that incorporate the associated fire protection measures.

Figure 2 outlines a process for approaching the risk profile and the incorporationof the related fire protection measures. It also shows how the risk profile can bechanged by the addition of sprinklers compensating for a shortfall of otherrecommendations.

A checklist for the design assessment stated in Figure 2 is highlighted in Table 5.


Methodology and tactics for use of the standard

Determine risk profile

Is minimum package of fire protection measures available? (See Chapter 5, Table 6)

Design assessment

Does the design conform to the means of escape, construction, operational and fire-fighting requirements of the standard (see Table 5)?

Introduce additional fire protection measures

No – Option 2

OK

No – Option 1

Yes

No

Consider adding sprinklers to reduce the risk profile or an alternative fire engineering approach

Yes

Figure 2 – Process for approach to risk profile and related fireprotection measures

© Buro Happold



Factor Comments

Adequacy of means to prevent fire The assessment should identify thescope for fire prevention measures andindicate the associated managementsystems needed.

Early fire warning by an automaticdetection and warning system toenable early evacuation

This provision can also lead to ‘first aid’or fire and rescue service fire-fightingin the early stages of fire development.Modern systems can be unobtrusive(aspirating), addressable (by which afire location and development can beidentified) and can reduce unwantedalarms.

The standard of means of escape See Chapter 6 and Chapter 8 (for whichstructural enclosure and separationwould be a part).

Provision of smoke control See Chapters 7, 9, 10 and 11.

Control of the rate of fire growth This item particularly includes spreadof flame over surfaces and linings, andwithin contents. See Chapter 8.

Adequacy of the structure to resist theeffects of fire

See Chapter 8.

Degree of fire containment Includes containment bycompartmentation, cavity barriers,and fire stopping. See Chapter 8.

Fire separation between buildings orparts of a building

See Chapter 8.

Standard of active measures for fireextinguishment or control

See Chapters 4 and 8.

Facilities to assist the fire and rescueservice

See Chapter 7.

Quality of premises management See Chapter 5.

Provisions for staff training andongoing controls

See Chapter 5.

Occupancy characteristics and riskprofiles

See Table 3.

Table 5 – Checklist for the design assessment (BS 9999: Table 1)

It is essential that any fire protection system that might be included because ofclient or insurance requirements or later sections of BS 9999 are identified priorto beginning the design assessment of the building to minimize abortive work.The impacts of such systems on design guidance are highlighted in theremainder of this chapter.

Inclusion of automatic sprinklers

As discussed in Chapter 2, when using BS 9999 the value of installing automaticsprinklers in a building is recognized by directly altering the risk profile throughreducing the fire growth rate by one level. It is therefore necessary to knowwhether the building being designed necessitates automatic sprinklers as aminimum provision to avoid abortive work.

In addition to client and insurance requirements, this can be due to the followingrecommendations within BS 9999: Section 7 Designing the Building Structure(refer to Chapter 8 of this handbook):

• All buildings with a floor greater than 30 m in height should be protectedthroughout by automatic sprinklers.

• Where there is a need to reduce the risk profile to comply with thecompartmentation guidance, see Chapter 8, Table 18.

• Certain basements that are >200 m2 in floor area and >3 m belowadjacent ground level (except for car parks) and are mechanicallyventilated.

• The risk profile for unacceptable conditions from Table 3 (A4, B4 and C4)should be changed.

Note that where sprinklers are necessary to meet the recommendations ofBS 9999: Section 7 Designing the Building Structure, the beneficial reduction offire growth associated with sprinklers can still be used to reduce the risk profile(refer to the worked example in Chapter 14).

Inclusion of automatic fire detection and alarm

The value of installing automatic detection and alarm in a room or space to ahigher standard than the minimum recommended is recognized within BS 9999by allowing the application of a per cent variation (stated as 15 per cent) to thefollowing components of the means of escape design:



• travel distances (15 per cent increase, refer to Chapter 6);• horizontal escape route widths (15 per cent decrease, refer to Chapter 6);• escape stair widths (15 per cent decrease, refer to Chapter 6).

Note that the per cent variation is allowable only where automatic smokedetection and alarm within the room or space is not required as a minimumprovision by the standard (refer to Chapter 4 of this handbook) and a clearbenefit can be demonstrated (refer to the worked example in Chapter 15). Forexample, the installation of automatic smoke detection within a small receptionarea is unlikely to provide a direct benefit to the persons in the reception, but itmay provide a clear early warning of a fire in that area for those persons locatedin adjoining spaces. Similarly, a fire warning system that provides informationabout a fire incident can greatly reduce the response of the occupants withinthe building. However, the installation of a voice alarm system is likely toprovide a greater benefit in a building containing occupant characteristic B. In abuilding with occupant characteristic A, where the occupants are familiar withthe building layout and receive regular training, they are likely to respondrelatively quickly to a fire alarm and the installation of a voice alarm is less likelyto provide an increased benefit compared with typical sounders.

Taking advantage of high ceilings

BS 9999 also recognizes the inherent safety associated with high ceilings withina room or space by allowing the application of a per cent variation (variabledependent upon the height) to the following components of the means ofescape design:

• Travel distances (per cent increase, refer to Chapter 6).• Horizontal escape route widths (per cent decrease, refer to Chapter 6).• Escape stair widths (per cent decrease, refer to Chapter 6).

Example of the application of the allowable variations andthe associated benefits

Figure 3 illustrates the potential flexibility and tangible benefits that can beachieved with the use of BS 9999. It compares an office with and withoutsprinkler protection, risk profiles A1 and A2 respectively. The immediatedifference between the two is likely to be a smaller number of escape routeswithin the building. The addition of automatic detection and alarm would result





Office without sprinklers – risk profile A2 Office with sprinklers – risk profile A1

≤ 55 m ≤ 65 m

Add automatic detection and alarm

Fire resistance periods between 15 min and 90 min (Table 16) No limit on building height No limit on compartment floor area Travel distance limited to 65 m

≤ 74 m

Add automatic detection and alarm

≤ 63 m

≤ 55 m ≤ 65 m

≤ 74 m ≤ 63 m

Automatic detection and high ceilings

≤ 90 m ≤ 75 m

Fire resistance periods between 30 min and 150 min (Table 16) Building height limited to 30 m unless sprinklers are provided No limit on compartment floor area Travel distance limited to 55 m

Actual allowable travel distance depends upon the height of the ceiling Overall travel distance limited to 90 m Total stair width required less than scenario B

Actual allowable travel distance dependsupon the height of the ceiling Overall travel distance limited to 75 m Total stair width required less than scenario B

Automatic detection and high ceilings

≤ 90 m ≤ 75 m

Travel distance limited to 74 m Total stair width required less than scenario A

Travel distance limited to 63 m Total stair width required less than scenario A

Scenario A

Scenario B

Scenario C

Escape stair cores

• •

•

•

•••

••

••

•

•

•

•••

Figure 3 – Design options© Buro Happold

in an increased travel distance and a reduction in stair and exit widths.Combining this with high ceiling heights could further increase the traveldistances and may result in a further reduction in the number of escape routes.

Multi-space buildings with various risk profiles

The guidance within BS 9999 is mapped against the risk profile. It is possiblethat a building will contain more than one risk profile, each with differentrecommendations, which may affect only the immediate locality of the riskprofile or apply to the entire building.

Where guidance affects the entire building, the most onerous recommendationrelating to the occupying risk profiles should be adopted throughout thebuilding. The following are examples of such design recommendations withinBS 9999:

• minimum level of management;• automatic alarm and detection;• emergency lighting;• fire resistance period;• compartment dimensions.

Where guidance affects the immediate locality of the risk profile, each spaceshould be assessed independently to determine the recommendations relevantto the associated risk profile. This assessment should also include any allowablevariations as these are dependent upon both the risk profile and the geometryof the space. The following are examples of such design recommendationswithin BS 9999:

• travel distances;• horizontal escape route widths.

Escape stair widths will often link different risk profiles and will require bothlocal and overall checks to assess the requirements.

Chapter 15 provides a worked example which highlights how therecommendations of BS 9999 can be applied to a building containingmultiple-risk profiles.



4. Allocation of fire protection measures

Key points

• A minimum level of management is expected for each risk profile withinBS 9999, with some necessitating higher levels than others. This minimumexpectation should be communicated to the intended user, to theirrepresentative or to those who will eventually co-ordinate the design withthe building operator/end user/client.

• Minimum levels of fire detection, alarm and emergency escape lightingcoverage are expected within BS 9999, with the extent being dependentupon the risk profile.

• Table 6 highlights the minimum fire protection measures that arenecessary for each risk profile.

• The addition of sprinklers improves safety, changes the risk profile andtherefore might allow reduced minimum fire protection measures.

• Where the minimum fire protection measures cannot be provided, a fireengineering approach should be adopted (refer to Figure 2).

Refer to Chapters 6, 7 and 8 of this handbook to identify the minimumrecommendations for means of escape, fire-fighting facilities and buildingconstruction.

Background

For every risk profile there is a minimum package of fire protection measuresand a related management level that is necessary to ensure sufficient time forescape in the event of a fire. It is a basic requirement that will allow the designparameters for means of escape, construction, etc. to be adopted. The totalpackage of fire protection measures for each of the risk profiles is summarizedin Table 6 and represents the minimum necessary to allow the use of theBS 9999 approach.

The type and extent of fire detection and alarm is dependent on the risk profile.In premises where occupants are awake and the fire growth rate is low then itmay be acceptable to rely on manual detection. Where the fire growth rate ishigh, or occupants are asleep, fire and smoke spread may adversely affect



Allocation of fire protection measures

A1 M Underground or windowlessaccommodation

Stairways in a central coreor serving storey(s) morethan 18 m above ground

Internal corridors more than30 m long

Open-plan areas of morethan 60 m2

3A)

A2 M 2

A3 L2 1

A4 N/A N/A

B1 M All escape routes, includingexternal routes (except inshops of three or fewerstoreys with no sales floormore than 280m2 providedthat the shop is not arestaurant or bar)

2

B2 M 2

B3 L2 1

B4 N/A N/A

Ci1 Au/tomaticfire detectionin individualunits

All common escape routes,including external routes,except in two-storey blocksof flats

2

Ci2 Automaticfire detectionin individualunits

1

Ci3 L3 1

Cii1 L2 2

Cii2 L2 1

Cii3 L1 1

Ciii1 L1 2

Table 6 – Summary of the minimum fire protection package for eachrisk profile (BS 9999: Tables 6, 8 and 9)

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occupants remote from the area of origin of the fire, and automatic detectionand alarm are necessary to ensure sufficient time for escape in the event of afire. The provision of voice and/or visual alarms within buildings containingoccupancy characteristic B is not necessarily required as a minimum although itcan help to reduce evacuation time.

The lighting of escape routes should be such that occupants can move safelyalong the required escape routes during an emergency. It should be designed tooperate during failure of the normal power supply.



Ciii2 L1 All common escape routes,including external routes,except in two-storey blocksof flats

1

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C4 N/A N/A

Generallyfor anyuse

All sanitary accommodationwith a floor area over 8 m2.Windowless sanitaryaccommodation with afloor area not more than8 m2. Electricity andgenerator rooms. Switchroom/battery room foremergency lighting system.

Emergency control roomA) Level 3 provides a very basic level of management and in some instances may not be

adequate to meet other legislative requirements, i.e. the Regulatory Reform (Fire Safety)

Order in England and Wales.

Table 6 – Summary of the minimum fire protection package for eachrisk profile (BS 9999: Tables 6, 8 and 9) (contd)

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Access and facilities for fire-fighting are not currently aligned to the riskprofiles although this could happen at a future time. However, in carrying outa fire-fighting risk assessment for a particular building some consideration couldreasonably be given to the risk profile and the associated fire protection measuresas part of the assessment.

The management of fire safety is discussed further in Chapter 5.

Additional fire protection measures

In addition to the variation of risk profile enabled by the addition of sprinklers,the design can be varied further to account for high ceilings, which increasethe smoke fill time and therefore the time available for means of escape (seeChapter 1 on spread of fire and smoke). The design can also be altered byadding automatic fire detection to increase the travel time to escape.

These additional measures affect only the means of escape design and aretherefore described in more detail in Chapter 6.



5. Managing fire safety – design,occupation and construction

Key points

• A building should be designed such that it can be managed, and thereforefire safety management should be a consideration right from the earlystages.

• Management levels are dependent upon occupant characteristics and fireloading and therefore form part of the minimum fire protection measuresassociated with a risk profile (refer to Table 6).

• There are three management levels in BS 9999, levels 1, 2 and 3; level 1 isthe highest (with expectation of empowerment and resource) and level 3is the lowest.

• There are several key factors that must be taken into account whendeciding upon a management level, and these are outlined in Table 7.

• The client should develop a fire safety policy to inform the designers andcontractors of their fire safety requirements.

• Designers and/or contractors are responsible (e.g. requirement underRegulation 16B of the Building Regulations in England and Wales) forproviding all fire safety related design and as-built information on projectcompletion such that clients can incorporate it within their fire safetymanual.

• The client should produce a fire safety manual to integrate the fire safetypolicy, the information provided by the designers and/or contractor, andthe proposed operational organization and plan. This will contribute toany risk assessment required under current UK legislation, e.g. TheRegulatory Reform (Fire Safety) Order in England and Wales.

Background

It is a fundamental assumption that the measures described in BS 9999 willrequire management and maintenance throughout the life of the building.Once the designer and/or contractor have handed over the building then goodmanagement of fire safety becomes the key element to fire safety throughoutthe life of the building. It is therefore essential and safer if management


activities are explicit and are used positively rather than undervaluing what goodmanagement can deliver.

‘Managing fire safety’ refers to a whole process throughout the life of a building,starting with the initial design, which is intended both to minimize the incidenceof fire and to ensure that, when a fire does occur, appropriate fire safety systems(including active, passive and procedural systems) are in place and are fullyfunctional. The management of fire safety is thus an essential element inaverting disaster in the event of a fire. Although many buildings will never havea serious life-threatening fire, it is essential for fire safety procedures to beplanned for every building. It is now widely acknowledged that effectivemanagement of fire safety, system maintenance, staff training, etc. is integral tothe design and engineering for life safety throughout the life of a building.

Effective management of fire safety can contribute to the protection of theoccupants of the building in many ways:

• by working to prevent fires occurring;• by monitoring the fire risks on an ongoing basis and taking appropriate

action to eliminate or reduce the risk;• by being aware of the types of people in the building (such as disabled

people, elderly people, children, pregnant women, etc.) and any special risksor needs;

• by ensuring that all of the fire safety measures in the building are kept inworking order and in particular that the means of escape are alwaysavailable;

• by training staff and organizing the evacuation plan, to ensure thatoccupants leave quickly if a fire occurs;

• by taking command in the event of a fire until the fire and rescue servicearrives.

Management levels

In BS 9999, the standard or quality of management is referred to as themanagement level. There are three management levels: level 1 which providesthe highest level of management; level 2 which provides a normally acceptablelevel of management; and level 3 which provides a very basic level ofmanagement.


Managing fire safety – design, occupation and construction

The minimum acceptable level of management within a space or building isdependent upon the fire loading and the occupant category, the risk profile.Table 6 maps the minimum level recommended by BS 9999 to the various riskprofiles within the standard. However, irrespective of the guidance given inTable 6, it is important to ensure that the management level proposed doesreflect the intended use and operation in the building. A designer should bear inmind that a level 3 management system may not meet the requirements placedon the occupiers, owners or other responsible persons under current UKlegislation, i.e. the Regulatory Reform (Fire Safety) Order in England and Wales.

When considering the appropriate level of management within a space orbuilding there are several key factors that should be taken into account. Table 7highlights these key factors and what is expected for the three managementlevels in relation to each of these factors.

In the UK, the management for fire safety has been present for some time now, butthere is still not sufficient confidence to use a management level as an ‘additionalmeasure’ as defined by BS 9999 at this point in time. Nevertheless the step taken toinclude management levels in BS 9999 is very important in emphasizing the value ofmanagement for delivering improved fire safety. However, looking forward, withincreased experience and the application of the Regulatory Reform (Fire Safety)Order in England and Wales, the recognition of fire safety management as anadditional benefit is a goal for the future. With the appropriate risk assessment,fire safety management can be part of a fire safety engineered approach.

Designing so that a building can be managed

Management, working in combination with the right package of fire protectionmeasures, is fundamental to fire safety in the built environment. It is importantto emphasize that reliance cannot be placed on active and passive fire protectionmeasures alone. A design that relies on an unrealistic or unsustainable managementregime cannot be considered to have met the requirements of Part B of theBuilding Regulations.

Where the designer is aware of the management systems that will be adoptedin the premises upon occupation, they can be taken into account in the firesafety design strategy. Where the management systems are not known, thedesigner will need to specify the management level that is appropriate for thedesign. During the life of a building the management level may need to bechanged to reflect new circumstances or a change of risk profile.



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Level 1 Level 2 Level 3

Planning for riskprofile change

Planning anticipates the impactof any proposed changes to therisk profile and identifies anyalternative protection andmanagement measures requiredas a result and ensuresimplementation.

This level reacts to the impact ofproposed changes to the riskprofile, identifies alternativeprotection and managementmeasures required and ensuresimplementation.

This level reviews any changes ona periodic basis, identifiesalternative protection andmanagement measures requiredand ensures implementation.

Resources andauthority

Manager(s) are empowered toensure that legislative fire safetyrequirements are met; theyinitiate testing, initiatemaintenance or repair, and havedirect control of staff responsiblefor these tasks. Powers aresupported by appropriateresources and funding. Note thatin companies operating overseveral locations some fire safetymanagement actions may becontrolled from a central point(head office). Where this is thecase the local and central powersshould be co-ordinated to ensurethat the outcome is to asufficient standard to meet thelocal needs.

Responsibility is divided over anumber of different individuals,departments or even companies.Implementation of changesrequires approval of those notdirectly responsible formanagement of fire safety withinthe premises.

Persons responsible for fire safetyhave limited power or resourcesand are unlikely to ensure thatthe fire safety systems are keptfully functional without referenceto a third party.

Table 7 – Key factors used in assessing management levels

32The

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Level 1 Level 2 Level 3

Staffing levels Staffing level is specific to thebuilding considering: use ofbuilding, nature of occupants,management systems in place,active and passive fire systems,and includes sufficiently trainedpersonnel to ensure occupantsare assisted out of the buildingeffectively in an emergency andincludes contingency for training,sickness and other unexpectedabsences.

As for Level 1, except that therewill be no contingency provision.

General training is provided on aperiodic basis.

Fire training This level ensures sufficient staffnumbers are trained in all aspectsof fire prevention, fire protectionand evacuation procedures, withcontingency for sickness orholiday.

As for level 1, except there will beno contingency provision.

Work control is developedproactively with clear lines ofresponsibility, a permit system,logging and audit processes, androutine checking and supervision.

Work control Work control is developedproactively with clear lines ofresponsibility, a permit system,logging and audit processes, androutine checking and supervision.

Work control is developedreactively with clear lines ofresponsibility with a permitsystem and logging and auditprocesses.

Work control is reactive to workrequired on site.

Table 7 – Key factors used in assessing management levels (contd)

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Communicationprocedures

Communications ensure thatthose involved are giveninformation, which includes useof alternative formats andcontingency for systems failure.

As for level 1, except there will beno contingency provision.

As for level 2, except that it doesnot allow alternative formats.

Maintenanceand testing offire systems

Dynamic monitoring of fire safetysystems and equipment isfunctional at all times when thebuilding is in use and includesalternative procedures for timeswhen systems and equipment areunavailable or not fullyfunctional.

Monitoring of fire safety systemsand equipment is functional at alltimes when the building is in use.Alternative procedures for timeswhen systems and equipment areunavailable are determinedreactively.

A predetermined regime ofmaintenance and testing is not inplace.

Fire authorityliaison

Liaison is proactive and includesnotification of the fire authorityto changes in risk profile andother key factors, and routinemeetings.

As for level 1, except there will beno routine meetings

Liaison is likely to be eithernon-existent or sporadic.

Contingencyplanning

Planning is proactive and takesaccount of a wide range ofpossible emergency incidents.

Planning takes account of anarrow range of possibleemergency incidents.

There is no effective pre-planningand ongoing business continuityis unlikely to be secured.

For example, where reductions in management levels from those adopted withinthe original design strategy are proposed, there will be a need to re-evaluate thefire safety strategy for its continued viability. Similarly, changes to the buildinglayout might require changes to the management procedures. This is a legalduty for the employer, building owner or occupier under the Regulatory Reform(Fire Safety) Order.

The primary objective is to design a building that can be managed andmaintained with an adequate level of fire safety that meets the needs for aneffective and efficient building that complies with the client brief. This isachieved by:

• the client developing a fire safety policy to inform the client brief;• providing a level of management that is consistent with the risk profile;• designing and constructing a building that complies with the client brief;• the operator/end user/client procuring and owning an up-to-date fire safety

manual, which reflects the original design intent and any subsequentchanges to the building or use.

The interaction of the above points during the design and construction processis highlighted in Figure 4 as is the associated legislation that drives them. Theway that buildings are procured and delivered to the eventual user variesconsiderably as do the parties that are responsible for delivering the variouscomponents highlighted in Figure 4. Therefore, the leader of the design,procurement and operational stages needs to be aware of the main requirementsso that they can be passed on effectively throughout the process as differentparties get involved.

Fire safety manual

The design of buildings needs to be documented for the benefit of themanagement of the premises. All relevant information should be included ina fire safety manual. The manual needs to set out the basis on which the firesafety design was planned, the type of management organization envisagedfor running the building and the consequential staff responsibilities. It needsto explain the operation of all the mechanical and electrical systems and to giveinformation on routine testing and maintenance requirements. The assumptionsmade at the design stage regarding these aspects should be recorded in the firesafety manual.





Design Construction Client/operator

Fire safety policy

Fire safety design process

Construction information

Fire safety plan for construction

Building Regulations

Health and Safety (CDM)

Operator/client/end user responsibility (controlled by the Regulatory Reform (Fire Safety) Order in England and Wales)

As-built fire safety information

Client brief

Continued update of fire safety policy to reflect design development and construction

Fire safety

manual

Risk assessment

Operational organization and plan

Construction

Figure 4 – Process to design and construct a building that can bemanaged

© Buro Happold

The operator/end user/client should at the outset of a construction project,new-build or refurbishment define a fire safety policy that can inform the brieffrom the client to the design (and construction) team. Initially this policy maysimply be a set of strategic statements or objectives, but during the life of theproject it should be continually updated to reflect design progression andconsultations with external stakeholders such as insurers, funders and approvingauthorities. The fire safety policy, via the client brief, can be the vehicle forensuring that the appropriate information is provided by the designers and/orcontractors to the client at project completion for incorporation into the firesafety manual.

During the design and construction stages of a project, the fire safety designstrategy should be continually reviewed, and regularly documented, such thatat project completion, up-to-date documentation is available for incorporationinto the fire safety manual by the client. In addition to the fire safety designstrategy, it is the responsibility of the designers and/or contractor (e.g. requiredby Regulation 16B of the Building Regulations in England and Wales) to provideall other necessary as-built fire safety-related information, i.e. systems and equipmentmanuals, etc., to the client for incorporation into the fire safety manual.

On large and complex projects a considerable amount of material needs to beunderstood and responded to by the client, who either needs to make sure thatthere is sufficient ‘in house’ expertise, or that appropriate experts are appointed.Wherever possible the opportunity should be created to introduce an overlapbetween the design, construction and the development of the fire safety manualleading to effective operational planning.

The following outlines a potential structure for the development of the firesafety manual document:

1. Fire safety policy; includingc strategic client fire safety performance objectives;c aims of proposed management system;

2. Design information; includingc fire safety design strategy;c details of as-built fire safety systems;c testing and maintenance requirements;

3. Operational organization and plan; includingc operational records;c responsibility of management and staff;



c evacuation planning;c assessment against fire safety policy.

4. Review and maintenance of fire safety manual; includingc building alterations;c changes in staff duties and training;c responses to incidents.

The fire safety manual should form part of the information package that contributesto any fire risk assessment that might need to be carried out, i.e. under theRegulatory Reform (Fire Safety) Order in England and Wales. The fire safetymanual, its contents, use and upkeep should conform to the recommendationsgiven in BS 9999: Annex H.



6. Design for means of escape

Key points

• The occupancy characteristics, fire growth rate and risk profile arefundamental to the design for means of escape (refer to Chapter 2).

• The recommended travel distances and width per person for escaperoutes are only applicable when the minimum fire protection measuresare provided (refer to Tables 9, 10 and 12).

• High ceilings and additional fire protection measures, such as automaticfire detection and alarm, allow variations to the recommended traveldistances and escape width.

• The percentage variations should be summed and checked against theallowable limits for travel distance and escape width.

• The addition of sprinklers improves safety, changes the risk profile andtherefore allows increased travel distances and reduced escape widths.

• Where the proposed means of escape design will not meet with therecommendations of the standard, a fire engineering approach should beadopted (refer to Figure 2).

Background

The package of fire precautions provided for a building should reflect the natureof the use of the building, the occupants, processes, materials stored and used,and the fire safety management provided (see also Chapter 5). Risk profilesprovide a basis against which the ‘risk to occupants’ can be assessed and theappropriate level of fire precautions determined. See Table 6 for the processlinking risk profile to design for means of escape.

Reasonable facilities for means of escape in fire are necessary to limit thedistance travelled by occupants directly at risk from the fire and the smoke, andsubsequently structural fire precautions are required to safeguard escape routes.In densely occupied spaces the critical condition will be queuing so the width ofexit doors, corridors and stairs will be the primary concern. In lightly occupiedspaces the critical factor will be the distances to the exits. Escape routes from astorey should be sited so that a person confronted by fire can go around thesource if distances are short or otherwise turn away from the fire and take a saferoute through an alternative exit.


The basic assumption is that no reliance should be placed on fire and rescueservices. Special consideration will be necessary in certain institutional buildingswhere assistance from staff may be necessary. Additional consideration will alsobe necessary for people with disabilities.

The guidance in Chapter 5 enables the allocation of the risk profile appropriatefor the intended use of a given building, which is in effect the first stage of riskassessment to align the building design with the intended operation. Associatedwith each risk profile is a package of fire protection measures that are consistentwith the risks associated with the particular occupancy characteristic and the firegrowth rate (Table 6). Similarly for each risk profile a set of means of escapedesign rules need to be applied as summarized in this chapter.

Planning for means of escape has a major impact on a building design, and soserious consideration needs to be given to identify the most appropriate strategyto adopt. The range of options can include the following, which is not exhaustive:

• total simultaneous evacuation involving immediate evacuation of all occupants;• total simultaneous evacuation involving two stages with the first being an

investigation period;• total evacuation carried out in a series of phases that reduces the total width

of protected stairways, but require additional active and passive fireprecautions supported by management procedures to ensure the safedelivery of the phased evacuation plan;

• progressive horizontal evacuation from the fire-affected compartment to anadjacent place of safety in a fire compartment at the same level;

• zoned evacuation to places of relative safety within a large space, such as ashopping complex – a possibility that is beyond the scope of this handbookand is likely to require a fire safety engineering approach.

The development of the building plan and design for means of escape is anintegrated exercise that can be facilitated flexibly by providing additional fireprotection measures as set out by the standard. The choice of internal subdivisions(compartments, partitions, atria, etc.) within a building align to the spatial/visualplanning and will clearly have an impact on the design for means of escape, soearly consideration will deliver considerable benefit to the design process.

Particular points to note in relation to the design for means of escape include:

• identification of any high-risk fire areas that need special consideration – seeBS 9999: Clauses 13.6 and 15.2


Design for means of escape

• provision of crèches adjacent to escape routes that would be used by theparents; see BS 9999: Clause 14.1 (b).

• provision of additional fire protection measures for disabled people toimprove communications, CCTV extensions, places to rest, additionalhandrails plus additional way finding and warning;

• progressive horizontal evacuation using fire compartments is an acceptablemeans of escape for disabled people in all risk profiles;

• simultaneous evacuation to be adopted for all basement storeys andbuildings incorporating openings between floors (excludes those suitablydesigned in accordance with BS 9999: Annexes B and C);

• exits to be discounted in turn when sizing escape routes to ensure adequateescape during a fire. It is not necessary to discount an entire escape stair in asprinkler-protected building or where that stair is protected by either lobbiesor a pressurization system (note that storey exits are still required to bediscounted in turn);

• final exits, not less than the escape routes they serve, to facilitate rapiddispersal of the occupants, clear of danger from fire and smoke, risks frombasements and with care to ensure space for wheelchair users;

• negotiating doors can be critical, so easily operated simple fastenings areessential. Where security conflicts arise consideration should be given toappropriately specified powered locks (see BS 9999: Clause 16.5.2 andBS 7273-4: 2007). In empty non-residential buildings final exit locks may beacceptable subject to appropriate management procedures.

The means of escape recommendation on distance and door widths arealigned to an engineered approach while respecting the considerable amountof knowledge in documents such as Approved Document B and BS 5588.Minimizing the time taken for the total evacuation to a reasonable level is thekey to a successful outcome. Therefore any engineered approach has to rely ontime as the basic control for making recommendations. Some of the factors thatinfluenced the outcomes in the standard are listed below.

• A fast-growing fire results in less time being available for escape.• The average speed for people who are unfamiliar is less than for those that

are familiar and trained.• Sprinklers reduce the fire growth rate but do not necessarily extinguish the fire.• In large rooms the time taken to commence evacuation can be much greater

than for small rooms where the risks are more quickly apparent.• Management plays an important role in ensuring an early commencement to

evacuation.



Figure 6 illustrates the broad relationship that exists between the pre-movementtime during the ‘available safe escape time’ (see Figure 7) and influences such asthe size of a room, the fire growth rate and the complexity of a space. Warningand alarm systems will have relatively little impact on smaller spaces and wherethe fire and smoke are clearly apparent. However, warning and alarm clearlybecome more important as the size and the complexity of a space increases.

Figure 7, a schematic representation of the assumptions that were made inthe determination of the range of travel distances in BS 9999, highlights therelationship with time, which clearly has a major impact on the safe means ofescape. Figure 6 presents the critical time periods during the means of escapeprocess in a building. The assumptions are summarized below.



Carry out risk assessment to prescribe Risk Profile accounting for presence of sprinklers (see Chapters 3 and 4)

Determine minimum package of fire protection measures associated with risk profile – Table 6

Carry out a design appraisal to assess if compliance with the minimum package of fire protection measures is achieved – Table 5

Design OK

Option 1 – Add sprinklers and review the risk profile (see Chapter 3)

Option 2 – Add additional fire protection measures and repeat process (see Chapter 4)

No No

Yes

Figure 5 – Design for means of escape – decision chart

© Buro Happold

• The time taken for people to start to move and escape (i.e. the pre-movementtime) is likely to be shorter if the fire is growing quickly and smoke or flamesbecome apparent, or are detected sooner.

• If a room is small, the time taken to react to a fire is clearly very short, as thesmoke fill time is very quick, and, so movement is more likely to begin duringthe incubation stage of a fire. (See Figure 6.)


Design for means of escapeH

eigh

t of s

mok

e ab

ove

floor

Small rooms

Medium rooms

Complex medium rooms

Large rooms

Complex large rooms

Pre-movement time

Slow growth fire

Medium

Fast

Base of smoke layer as fire develops

Figure 6 – Pre-movement time as a function of fire growth rate

© Buro Happold

• In medium and large spaces, the time to recognize the risks associated with afire will depend on the fire growth rate. Small slow-growing fires will not beseen or detected as a risk as quickly as fast growing fires.

• The more complex a space (in terms of its shape or due to obstructions) thelonger the time will be before a fire is recognized as a risk particularly by thepeople who are farthest away from the fire. Those people closest may wellstart moving sooner.

Additional fire protection measures

The provision of automatic sprinklers is covered in Chapter 3 and affects the riskprofile, which needs to be determined at an early stage. This should not beconfused with additional fire protection measures.



Available safe escape time (ASET)

Life safety strategy complete

Pre-movement time

Occupants become aware of fire by alarm or by observation of fire and/or smoke

Incubation period of fire following ignition

Actual travel time

Allowable travel time

Fire continues to grow with time

Time line

Tenability limits reached

Figure 7 – Fire growth, means of escape and travel time (adapted fromFigure 1, BS 9999)

Every building should incorporate the minimum level of fire protectionmeasures recommended in Table 6. However, if additional fire protectionmeasures are provided it is permissible to increase the travel distances andreduce the door widths and stair widths, subject to the maximum variationsgiven in the following paragraphs. Any such increase/decrease should, however,be carefully reviewed and assessed by the designers for applicability during therisk assessment process.

Effect of automatic fire detection

The provision of automatic smoke detection systems can be of significantbenefit in terms of providing early warning for the occupants. If such systemsare installed, they should be designed and installed in accordance withBS 5839-1. The speed of response is likely to vary with different types ofoccupancy: for example, in an office building where the occupants are familiarwith the building layout and receive regular training, they are likely to respondrelatively quickly to a fire alarm; whereas in a shop where the occupants areunfamiliar with the layout and focused on their personal business, they willrespond much more slowly and might not begin evacuation until requested todo so by the staff.

The response of occupants of a building is generally enhanced by theinstallation of a fire warning system that provides information about a fireincident. In circumstances in which the occupants might be unaware of a firethey will rely upon the level of information given by the warning system inmaking the decision to evacuate or not.

Depending on the type of occupancy and level of management within thebuilding, the provision of an automatic fire detection and alarm system,primarily utilizing smoke detectors and incorporating an informative warningsystem (such as a voice alarm), might allow longer travel distances and narrowerdoors. Where automatic fire detection and alarm is necessary as part of theminimum package of fire protection measures recommended in BS 9999:Clause 16, a variation of the recommended travel distances, door widths,corridor widths and stair widths is not permitted. However, where a clearbenefit resulting from additional detection and/or enhanced warning systems isdemonstrated and is appropriate to the circumstances, a 15 per cent increase inallowable travel distance and a 15 per cent reduction in door width, corridorwidth and stair width is allowable.



Effect of ceiling heights

Rooms with high ceilings are safer than rooms with low ceilings, as they have agreater capacity and therefore increase the time taken to fill with smoke to alevel that affects escape.

For rooms with high ceilings, it is permissible to increase the travel distance anddecrease the door width, corridor width and stair width, provided that theincrease/decrease is no more than the percentages given in Table 8 and that theentire escape route, with the exception of protected corridors and protectedlobbies, has a high ceiling. This flexibility is appropriate only when a full accountis taken of the risk presented, i.e. position, height and nature of fire load.

The height of the room should be measured to a point below significantobstructions such as downstand beams.



1. Room height

m

Maximum permissible increase in travel distance andreduction in door width, corridor width and stair width

All risk profiles except A4,B4 and C4A)

%

Risk profiles A4, B4 and C4A)

%

�3 Not allowable Not allowable

>3, �4 5 Not allowable







>10 30 Not allowable

A) These risk profiles are outside the scope of BS 9999. Addition of an effectivelocalized suppression system or sprinklers will reduce the fire growth rate andconsequently change the risk profile. Alternatively a fire engineering approach may

Table 8 – Permissible variation of door, corridor and stair widths andtravel distance with ceiling height (BS 9999: Table 16)

Maximum acceptable variations

The per cent variations for ceiling height and fire detection can be aggregatedsubject to not exceeding the maximum allowed as defined in Tables 9, 10, 11and 12.

Travel distance

The travel distance should generally not exceed the values given in Table 9for the appropriate risk profile. Note that Table 9 has two columns; the firstrecommends travel distances where the minimum fire protection measures areprovided and the second places a maximum if additional fire protectionmeasures have been provided to increase travel distances.



Riskprofile

Maximum travel distance whenminimum fire protectionmeasures are provided

Maximum permissible traveldistance – upper limit withadditional measures

Two-way travelm

One-way travelm

Two-way travelm

One-way travelm

A1 65 26 90 30

A2 55 22 75 24

A3 45 18 60 22

A4 Not applicable Not applicable Not applicable Not applicable

B1 60 24 90 28

B2 50 20 75 24

B3 40 16 60 20

B4 Not applicable Not applicable Not applicable Not applicable

C1 27 13 37 18

C2 18 9 27 13

C3 14 7 18 9

C4 Not applicable Not applicable Not applicable Not applicable

Table 9 – Travel distance as a function of risk profile(BS 9999: Tables 12 and 17)

Door and escape stair widths

The width of escape routes should not be less than the values given in Tables10, 11 and 12 for the appropriate risk profile and route component. Notethat Table 10 has two columns outlining the minimum width per person; thefirst recommends minimum door widths where the minimum fire protectionmeasures are provided, and the second places a lower limit if additional fireprotection measures have been provided to decrease escape widths.

Note that the absolute minimum width of doors and corridors is 800 mm and1,200 mm, respectively, irrespective of the calculated width.



Riskprofile

Minimum door width per personwith minimum fire protectionmeasures

mm per person

Minimum permissible doorwidth – lower limit withadditional measures

mm per person

A1 3.3 2.4

A2 3.6 3.0

A3 4.6 4.1

A4 Not applicable Not applicable

B1 3.6 2.4

B2 4.1 3.3

B3 6.0 5.3

B4 Not applicable Not applicable

C1 3.6 2.4

C2 4.1 3.3

C3 6.0 5.3

C4 Not applicable Not applicable

Table 10 – Door width as a function of risk profile – mm per person(BS 9999: Tables 13 and 18)

The minimum width of an escape stair when additional fire protection measureshave been provided to decrease escape widths should be not less than each ofthe following:

• the absolute minimum stated in Table 11; and• the available width per person should be not less than 75 per cent of the

appropriate value in Table 12.

Floor space factors

A realistic estimate should be made of the maximum occupancy associated withthe intended use of the room/space. This can be achieved by either using themaximum number of persons the room/space is designed to hold or dividingthe area of the room/space by an appropriate floor space factor (see Table 13,although this list is not exhaustive and should not be prescriptively appliedwithout due consideration). Note that maximum limitation on the occupancyof any space is ultimately determined by the available exit widths provided.

Alternative escape routes

Where alternative escape routes are provided within a room they should besited so as to minimize the possibility of multiple exits being renderedunavailable simultaneously. Alternative escape routes should therefore meetthe recommendations outlined in Figure 8.




Width of stair fordownward travel

mm

Width of stair forupward travel

mm

A 1,000 1,200

B (except assembly) 1,000 1,200

B (assembly only) 1,100 1,200

C 1,000 1,200

Table 11 – Absolute minimum width of stairs (BS 9999: Table 14)

TheBS

9999H

andbook49

Desig

nfo

rm

eans

of

escape

Riskprofile

Minimum width of stair per person served over total number of floors served

mm

1 floor 2 floors 3 floors 4 floors 5 floors 6 floors 7 floors 8 floors 9 floors 10+ floors

A1 3.90 3.40 2.95 2.45 2.15 2.00 1.80 1.70 1.50 1.40

A2 4.50 3.80 3.25 2.75 2.45 2.20 2.00 1.90 1.70 1.60

A3 5.40 4.60 4.00 3.50 3.10 2.80 2.60 2.30 2.10 2.00

A4 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

B1 4.20 3.60 3.10 2.60 2.30 2.10 1.90 1.80 1.60 1.50

B2 4.80 4.00 3.40 2.90 2.60 2.30 2.10 2.00 1.80 1.70

B3 7.00 6.00 5.30 4.60 4.20 3.70 3.40 3.10 2.80 2.60

B4 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

C1 4.20 3.60 3.10 2.60 2.30 2.10 1.90 1.80 1.60 1.50

C2 4.80 4.00 3.40 2.90 2.60 2.30 2.10 2.00 1.80 1.70

C3 7.00 6.00 5.30 4.60 4.20 3.70 3.40 3.10 2.80 2.60

C4 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

NOTE The widths of stairs have been calculated on the assumption that all floors are evacuating simultaneously. This isconservative, as the occupants on the fire floor are likely to move more quickly than those on the other floors..

Table 12 – Minimum width of escape stairs for simultaneous evacuation (BS 9999: Table 15)



Occupancy Floor spacefactor

m2 per person


m2 per person

Administration office 5.0 Individual seating 0.4

Amusement arcade 0.5 Indoor games/trainingrooms in schools

10.0

Archive/library readingarea

5.0 Kitchen 7.0

Art gallery 5.0 Licensed betting office(public area)

1.0

Assembly hall 0.5 Lobbies 2.0

Banking hall 3.0 Lounge 1.0

Bar 0.3 Machine/printingroom

10.0

Bazaar 2.0 Mechanical plantroom

30.0

Bench seating 0.4 Meeting room 1.0

Billiards or snookerroom

10.0 Museum 5.0

Bingo hall 0.5 Office (closed-plan orless than 60 m2)

8.0

Bowling alley 10.0 Office (open-plan orexceeding 60 m2)

5.0

Business centre 7.0 Queuing area 0.5

Car park (per parkingspace)

2.0 Reading or writingroom (seated)

2.0

Classroom 2.0 Reading room(standing)

1.0

Club 0.5 Reception area 2.0

Committee room 1.0 Restaurant 1.0

Common room 1.0 Shop 2.0

Table 13 – Examples of typical floor space factors (BS 9999: Table 10)




m2 per person


m2 per person

Computer room 7.0 Showrooms 7.0

Conference room 1.0 Skating rink 2.0

Crush hall 0.5 Space with looseseating

0.75

Dance area 0.5 Space with loosetables

1.0

Deposit/strongroom 30.0 Stadia andgrandstands

0.6

Design studio /Drafting office

7.0 Staffroom 1.0

Dining room andcanteens

1.0 Storage andwarehousing

30.0

Dining rooms withloose tables

1.0 Studio (radio,television, film,recording)

1.5

Dormitory 5.0 Teaching laboratories 3.0

Exhibition areas 1.5 Venue for popconcerts

0.5

Factory productionarea

5.0 Waiting area/visitors’lounge

2.0

Filing room/store 10.0 Waiting room 2.0

Foyers in theatres andcinemas

0.3 Workshop 5.0

Gymnasium – openplan (where fixedmachines are used,the occupancy isbased on the numberof machines provided)

0.6

Table 13 – Examples of typical floor space factors (BS 9999: Table 10)(contd)

Inner rooms

An inner room is an enclosed space that has only one escape route that passesthrough another room (access room) before reaching a corridor or storey/finalexit. Consequently, an inner room can be at risk if a fire starts in the accessroom. Therefore, in order to minimize the risk associated with an inner room,



A D

C

B

E

45º<45º

Alternative routes are available from C because angle ACB is 45° or more, and therefore CA or CB (whichever is the less) should be no more than the maximum distance for travel given for alternative routes.

Alternative routes are not available from D because angle ADB is less than 45°. There isalso no alternative route from E.

a) Option 1

A

B

D

C

45 ˚

Angle ABD should be at least 45°. CBA or CBD (whichever is less) should be no morethan the maximum distance of travel given for alternative routes, and CB should be nomore than the maximum distance for travel where there are no alternative routes.

b) Option 2 (travel distance in dead-end condition)

NOTE The use of dashed lines is to aid use of the diagrams and does not have anyother significance.

Figure 8 – Travel distance 45° or more apart (BS 9999: Figure 5)

such an arrangement is recommended only where all of the followingconditions are met:

• the occupant capacity of the inner room does not exceed 60 (30 where theoccupants require assistance to escape);

• the inner room is not a bedroom;• the inner room is entered directly from the access room;• the escape route from the inner room does not pass through more than one

access room;• the travel distance from any point in the inner room to the exit(s) from the

access room does not exceed the allowable one-way travel distance;• the access room is not a place of special fire hazard and is in the control of

the same occupier as the inner room;• one of the following arrangements is made:

c the enclosures (walls or partitions) of the inner room are stopped at least500 mm below the ceiling; or

c a suitably sited vision panel not less than 0.1 m2 is located in the door orwalls of the inner room, to enable occupants of the inner room to seewhether a fire has started in the outer room; or

c the access room is protected by an automatic smoke detector thatoperates either an alarm that is audible in the inner room, to a soundpressure level (typically measured in dB) in accordance with the minimumrecommended in BS 5839-1, or gives a visual indication in the inner roomif the ambient noise levels are so great as to make an alarm inaudible.



A B 2

1 3

Key 1 Room with alternative exits 2 Access room 3 Inner room

A needs no special provision. B should conform to the design recommendations above.

Figure 9 – Inner room and access room (BS 9999: Figure 6)

Dead-end corridors

All corridors serving a dead-end greater than 2 m should be protected with fireresisting construction. In addition, all dead-end corridors greater than 4.5 mthat are connected to more than one storey exit should be subdivided from theremainder of the corridor by fire doors (illustrated in Figure 10). Note thatwhere the corridor and any adjoining escape stairs are protected with a smokecontrol system using pressure differentials, then the latter recommendation forsubdividing fire doors can be omitted.

Progressive horizontal evacuation

The evacuation of occupants through one or more compartment walls within astorey is an acceptable form of evacuation and often may be the only approach



1

21 1 1

1 1

1 1

1

11

11

111

1

a) ‘T’ junction with main corridor b) Continuation past stairway

Key 1 Self-closing fire door 2 Fire-resisting construction (same fire resistance as protected corridor)

Protected corridor

NOTE Recommendations for fire resistance of fire doors (FD) and protected corridorsare given in BS 9999: Clause 32.1

Figure 10 – Dead-end corridors (BS 9999: Figure 9)

suitable for non-ambulant persons, i.e. wheelchair users, day-care patients,etc. The use of progressive horizontal evacuation using fire compartments isillustrated in Figure 11. For details of specific design recommendations forprogressive horizontal evacuation please refer to the BS 9999: Clause 17.3.13.

Escape for disabled people

Means of escape for disabled people may comprise a combination of structuralprovisions (e.g. lifts, refuge areas, ramps) and management procedures (e.g.assisted escape). A strategy should be designed to enable a flexible response todifferent situations.

The ideal methods of evacuation for disabled people are horizontal evacuationto the outside of the building or to another fire compartment, or verticalevacuation by lift.

Normal lifts should not typically be used for general evacuation, but in somesituations they may be used for the evacuation of disabled people where asuitable fire risk assessment is undertaken to evaluate whether the lift meets thefunctional recommendations of an evacuation lift. The risk assessment should



1

44 4

3 322

Key1 Compartment wall 2 Fire door (equivalent to storey exit) 3 Storey exit 4 Compartment

NOTE Travel distance limits apply to storey exits in compartment walls.

Figure 11 – Progressive horizontal evacuation (BS 9999: Figure 12)

take into account all the features of fire protection in a building. For example ina building with automatic sprinklers and significant compartmentation or smokecontrol, a risk assessment might conclude that a non-evacuation lift would beusable in the initial stages of a fire. Alternatively, specific evacuation lift(s) canbe provided within a building. Refer to BS 9999: Clause 46 and BS 9999: AnnexG for further guidance.

Where suitable lifts are not available then it might be necessary to carry disabledpeople up or down the escape stair. The management plan of a building shouldidentify the procedure to be used and staff should be adequately trained.

BS 9999: Annex G provides guidance on the design of refuges and evacuationlifts and BS 9999: Clause 46 provides guidance on the management ofevacuation for disabled people.



1

1

2

12

1

1,80

0

1,800

1,800

A

B

Dimensions in millimetres

Key 1 Accommodation 2 Stair

Fire-resisting construction

Figure 12 – External protection to protected stairways(BS 9999: Figure 14)



a) Example 1

1 2

34

5

5

6

7

1.8 m

A

BB

A

1.8 m

1.8

m

Plan

1.8 m 1

1.8 m

3

86

5

7Section A–A Section B–B

b) Example 2

Key1 No fire resistance needed for door 2 Window with 30 min fire-resisting construction 3 1,100 mm zone above top landing 4 1,800 mm zone of fire-resisting construction at side of stair 5 Self-closing fire door with 30 min fire-resisting construction 6 6 m maximum height of stair without weather protection 7 Ground level or a roof or podium served by an independent stairway 8 9 m zone of fire-resisting construction below stair

Figure 13 – Fire resistance of areas adjacent to external stairs(BS 9999: Figure 15)

External protection to escape stairs

Where an escape stair projects beyond or forms an angle* of greater than0 degrees with the adjoining external line of the building, then the distancebetween any non-fire-resisting area in the external wall of the building and anynon-fire-resisting area in the external wall of the escape stair should be at least1,800 mm (illustrated in Figure 12).

Where more than one escape route is available from a storey or part of abuilding and at least one of those escape routes is via an internal escape stair,other escape routes may be by way of an external escape stair providing theymeet the recommendations illustrated in Figure 13.



* NoteThe angle is that formed by the external face of the stair and the adjacent accomodation = 0° iswhere the external face of the stair and the façade enclosing the accomodation are directly in line.

7. Access and facilities for fire-fighting

Key points

• The recommendations for access and facilities for fire-fighting areindependent of the risk profile concept. Where it is proposed to vary theprovisions from those recommended within the standard, it is essentialthat early liaison and agreement is obtained from the fire and rescueservice.

• Fire-fighting shafts, including lifts, should be provided within all buildingsover 18 m in height.

• Additionally, fire-fighting shafts should be provided in shops, factoriesand assembly and recreation buildings >7.5 m in height and having floorareas �900 m2.

• Buildings between 11 m and 18 m in height and not meeting the previouspoint, should be provided with lobby protected escape stairs and internalfire mains.

• Fire-fighting shafts should be installed in basements of at least twostoreys, each having floor areas �900 m2. Fire-fighting lifts should beinstalled in basements deeper than 10 m.

• In buildings where internal fire mains are not provided, access to theperimeter of the building should be provided and be appropriate to theaggregate floor area of the building.

• Fire mains within buildings over 50 m in height should be of the wet type.• All shafts containing fire-fighting lifts should be designed to keep lift wells

free from water; this may include sloped floor/raised thresholds and/ordrainage channels at landing level or within the lift pit.

• Fire-fighting shafts serving buildings greater than 30 m above, or 10 mbelow, Fire service access level should be protected by a pressurizationsystem. All other fire fighting shafts should be provided with adequatenatural smoke ventilation (refer to BS 9999: Clause 28.2 for further details).

• Smoke and heat ventilation should be provided on all basement storeysthat have a floor area >200m2 and are >3m below adjacent grade level.

• Smoke clearance for fire-fighting should be provided in all atria notprovided with a smoke control system (see Chapter 9).

• Refer to BS 9999: Annex E for additional requirements relating toshopping complexes.


Background

The layout and design of a building should not only consider the escape ofoccupants from within, but also the ability of firefighters to enter and undertakefire-fighting operations in a reasonable period of time. The provisions needed toprovide appropriate access depend upon the size and complexity of thebuilding.

For low-rise buildings (up to three to four storeys) appropriate access can beprovided via the perimeter. However, as buildings with large floor platesapproach medium to high-rise or contain deep basements then access fromsolely the exterior is not practical and internal fire-fighting is necessary.

The method of vertical access for firefighters in medium to high-rise buildings isdriven by the fitness of individuals and their ability to climb several flights ofstairs before undertaking fire-fighting operations. Beyond a reasonable limit, it isnecessary to ensure appropriate vertical transportation, such as lifts, to assist inaccess.

In addition to vertical access, it is necessary to provide systems that allowefficient internal fire-fighting and adequate protection, such as mains to deliverfire-fighting water and a means of smoke venting.

Risk profiles and fire-fighting provisions

The recommendations for access and facilities for fire-fighting within BS 9999are independent of the risk profile concept and continue to use the purposegroups defined in Table D1 of Approved Document B. Where it is proposed tovary the provisions from those recommended, it is essential that early liaison isundertaken with the fire service. In varying the provisions, recognition should begiven to additional fire protection measures and factors that are built into therisk profile. The response of the fire and rescue services to an incident couldvary depending upon whether the occupants are familiar or unfamiliar. Thefire-fighting response will also vary with the quantity of fire load, the fire growthrate and the presence of sprinklers or other fire suppression systems. The use ofa fire-fighting intervention model could be used as part of such an assessment.Due consideration should also be given to a good management level where itcan be demonstrated to be beneficial to fire-fighting operations. For heritagebuildings the designers and the approving authorities would benefit by working


Access and facilities for fire-fighting

with the fire service to achieve the right pragmatic balance between active andpassive fire protection measures while respecting the historic surroundings.

Variation of the recommended provisions is currently beyond the scope of thestandard but could be considered in an alternative fire engineering approach.

External fire-fighting provisions

All buildings should have appropriate external access for fire service vehicles(appliances). This includes trafficable routes and hardstanding areas within closeproximity to building entrances and connection points to internal fire-fightingsystems.

In low-rise buildings it is possible to undertake fire-fighting operations via theexterior providing that sufficient access is available to the building perimeter.Buildings with a total floor area of 2,000 m2 or less and having a top storey notmore than 11 m above access level should be provided with vehicle access towithin 45 m of every point on the projected plan area of the building or to 15per cent of the perimeter, whichever is the less onerous. All other low-risebuildings should be provided with fire vehicle access to the perimeter ofbuilding in accordance with Table 14.

All elevations to which vehicle access is necessary should have a door(s) not lessthan 750 mm wide allowing entry to the interior of the building. Doors shouldbe located on the elevation such that there is no more than 60 m between eachdoor and/or the end of that elevation.

If the access outlined in Table 14 cannot be achieved, internal fire-fightingprovisions would be necessary. Note that where the standard recommendsinternal fire-fighting provisions for other reasons, Table 14 does not apply.However, where a building has internal fire-fighting provisions installed (seebelow), access for fire vehicles (pumping appliance) is necessary to within18 m of either each fire main inlet connection point for dry mains or the inletconnection point for emergency replenishment of the suction tank for the wetmains.

The specification of fire vehicle access routes and hardstandings should meetthe recommendations of BS 9999: Clause 22.3.



Internal fire-fighting provisions

As discussed above, buildings above a reasonable height or with deep basementsrequire an appropriate means of internal fire-fighting provisions and vary withheight and area of the building. Figure 14 summarizes the recommendations forinternal fire-fighting provisions.



Total floor areaof buildingA)

m2

Height to floor oftop storey ofbuilding

m

Type ofapplianceB)

Position of access

% of perimeterC)

<2,000 >11 Pump andhigh-reach

15

2,000 to 8,000 <11 Pump 15

>11 Pump andhigh-reach

50

8,000 to 16,000 <11 Pump 50


50

16,000 to 24,000 <11 Pump 75


75

>24,000 <11 Pump 100


100

NOTE 1 In the case of storage buildings, height should be measured to mean rooflevel.A) The total floor area is the aggregate of the floor areas of all the storeys in thebuilding.B) ‘Pump’ = pumping appliance; ‘high-reach’ = aerial appliance, e.g. turntable ladderor hydraulic platform.C) ‘Perimeter’ refers to the face of the total length of all exposed perimeter walls.

Table 14 – Perimeter access requirements for fire service vehicles(BS 9999: Table 21)



> –10 m

Fireserviceaccesslevel

>7.5 m

≥11 m

>18 m

>50 m

Key

Dry rising/falling fire

Wet rising fire main

Fire-fighting stair and fire-fighting lobby

Fire-fighting lift

Shops, factories or assembly and recreation with a floor area ≥ 900 m2

Basement floor areas≥ 900 m2

>30 m

Sprinklers recommended in buildings >30 m in height.

Pressurization recommended for fire-fighting shafts

i b ildi 30 i h i h

Hei

gh

t ab

ove

D

epth

bel

ow

Figure 14 – Summary of recommendations for internal fire-fightingprovisions

NOTES1. The number of fire-fighting shafts should be provided such that every part of thefloor plate is within the maximum hose distance requirements from the fire mainoutlet; 45 m for escape stairs and 60 m for fire-fighting shafts, and at least twofire-fighting shafts should be provided within buildings with a storey of 900 m

2

ormore in area.

2. Buildings not covered within the above figure should be provided with adequateperimeter access (refer to BS 9999: Clause 22).

3. Existing buildings, in particular historic buildings, may have difficulty incorporatingthe above recommended internal fire-fighting measures; therefore, alternative fireengineering solutions may be adopted. However, early consultation with the localfire service is recommended if an alternative needs to be adopted.

Where a fire-fighting shaft is recommended within Figure 14, then the layoutand fire resistance of the shaft construction should follow the principles outlinedin Figure 15. There are other recommendations within the standard on therobustness of the construction, refer to BS 9999: Clause 21.2.5.

The layout of any fire-fighting shaft at access level should be such that firefighterscan either enter directly from the open air or by way of a protected corridor notexceeding 18 m in length. Firefighters accessing the building should not obstructescaping occupants; therefore where an access route is shared with escapingoccupants it should be 500 mm wider than that necessary for means of escapepurposes (to allow room for fire and rescue service personnel to move towardsthe fire-fighting shaft).

Lifts designated for the use of firefighters can also serve the general buildingpopulation during non-emergency conditions. However, such lifts requireenhancement above a standard lift installation, such as protected powersupplies, protection from water ingress, etc., so that it can continue to operateduring emergency conditions. Therefore all lifts designated for firefighter useshould meet the recommendations of BS EN 81: Part 72, and BS EN 81: Part 1or BS EN 81: Part 2 as appropriate for the particular type of lift. Furtherguidance is provided by BS 9999: Clause 21.3.4.

Within large or complex buildings, a fire control centre should be providedto enable the fire service to co-ordinate fire-fighting and emergency operationseffectively. This can either be a dedicated room or combined within thesecurity/management control room. It should be located such that it is directlyaccessible from outside or accessible via a fire-protected route, and it should





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5 m

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4 5

6

4 elpmaxE )d3 elpmaxE )c

Key 1 Openable areas 2 Fire door with 30 min fire resistance with smoke seal 3 Fire-fighting lobby 4 Fire main 5 Fire door with 30 min fire resistance without smoke seal 6 Fire-fighting lift 7 Accommodation 8 Fire door with 60 min fire resistance with smoke seal

Minimum fire resistance of 1 h from both sides Minimum fire resistance of 2 h from outside the fire-fighting shaft and 1 h from

inside the fire-fighting shaft Minimum fire resistance of 2 h from accommodation

Figure 15 – Principles for the layout and fire resistance of fire-fightingshafts (BS 9999: Figure 16)

contain the status and override controls for all key fire protection systems.Further guidance on the design and content of fire control centres is provided inBS 9999: Clause 25.

Smoke control for fire-fighting shafts

All fire-fighting shafts serving floors greater than 30 m above, or 10 m below,Fire service access level should be protected by a pressurization system. All otherfire-fighting shafts should be provided with adequate natural smoke ventilation.BS 9999: Clause 28.2 has further guidance on the natural smoke ventilationoptions allowable.

Smoke venting from basement floors

Fire-fighting operations within basement storeys can be more hazardousbecause of the lack of self-venting that would typically occur through thefaçade on storeys above ground, leading to the build-up of smoke and heat.Therefore with the exception of basement storeys not more than 3 m belowthe adjacent ground level and with an area of not more than 200 m2, all otherbasement storeys should be provided with a system of smoke and heatventilation.

Natural smoke vents can be installed, provided that they are sited at highlevel, are evenly distributed and are equivalent to not less than 2.5 per cent ofthe floor area of each storey. The location of the smoke vents should be suchthat they do not prevent the use of escape routes from the building and thateach compartment within a basement is served independently, i.e. doorsbetween compartments should not serve as part of the route to external air.

An alternative to natural smoke vents is a mechanical smoke ventilation system.However, an automatic sprinkler system is required within any basement storeysserved by a mechanical smoke ventilation system. The system should be capableof providing 10 air changes per hour and begin operation automatically onactivation of the sprinkler system or an automatic detection system. BS 9999:Clause 28.3.3 provides further guidance.



Smoke venting from car parks, loading bays and serviceroads

The smoke ventilation for cark parks, covered service roadways and enclosedloading docks exceeding 200 m2 should be designed in accordance withBS 7346: Part 7.



8. Designing the building structure

Key points

• The occupancy characteristics, fire growth rate and the risk profile, arefundamental to the fire resistance for the building structure (refer to Chapter 2).

• Recommendations for minimum fire resistance periods for the relevantconstruction component are contained in Table 15.

• The availability of natural ventilation (windows and other non-protectedareas) on the building perimeter affects the recommended fire resistanceperiod. Where Table 15 refers to Table 16 for the recommended fireresistance period the room/space must meet the ventilation conditions inTable 17, otherwise further guidance from BS 9999 is required (see Figure 16).

• Maximum dimensions of compartments should meet therecommendations in Table 18.

• The addition of sprinklers improves safety and changes the risk profile,and therefore allows reduced fire resistance periods and increasedcompartment limits.

• All buildings with an occupied storey >30 m above access level shouldincorporate compartment floors and be protected throughout withautomatic sprinklers.

• Where the proposed construction design will not meet with therecommendations of the standard, a fire engineering approach should beadopted (refer to Figure 2).

Background

The fire performance of the building construction during a fire, for a reasonableperiod of time, is essential to protect the occupants, the firefighters and thoseexternal to the building who may be at risk from falling debris. This provision forlife safety clearly has a favourable impact on property protection, but specificrisk assessments will be required if there are particular needs for additionalprotection. As with all fires, there is considerable benefit for life safety, reducinginsurance risk and property protection if whole-life consideration is given to themanagement provision to reduce the chances of a fire starting and growing.


Where there is a need to protect heritage buildings in a sensible, practicalmanner, the flexibility allowed by BS 9999 can reasonably be adopted to createwell-judged holistic solutions.

The arrangement of the load-bearing and non-load-bearing construction/structureas dictated by the means of escape and the compartmentation provisions isclearly fundamental and covered by the guidance in those sections incombination with the recommendations that follow here.

There are a range of factors that have an influence on the fire resistancerequirement depending on the consequences of failure. The fire growth rateand the occupancy type, which are the two primary factors that drive the choiceof risk profile, plus the height and scale of a building, all have an impact on thefire resistance requirement. Sprinklers in many cases will have a beneficialimpact and will allow a reduction in the fire resistance performance of thestructure while maintaining the required standard.

The following are used to describe the fire resistance performance ofload-bearing elements of structure in a fire resistance test.

• Load-bearing capacity is the ability of a structure to carry the applied loads,while being acted on by fire. Traditional approaches to the design andanalysis of structures in fire are based on the behaviour of isolatedelements – beams, slabs and columns with idealized support conditionstested in a furnace. This is convenient for ‘proof testing’ and is consistentwith the approaches traditionally used for normal design at ambienttemperature, with no recognition given to real fire performance.

• Integrity is the ability of the structure to prevent the development ofsignificant-sized holes to limit the transmission of hot gases. Failure is relatedto openings forming in a member and defined by ignition of a cotton padheld close to an opening (testing method in BS 476). This reduces thechances of spread of fire and increases the chances of adjacent spacesremaining tenable. Voids in the construction for services or other purposesneed to be carefully detailed, usually by the architect, in accordance with theappropriate building code to prevent spread of fire around or through thestructure.

• Insulation is the ability of a structure to limit the transfer of heat withindefined limits so that fire does not spread and adjacent spaces do notbecome untenable. For insulation, the failure criteria are a temperature riseon the unexposed face of 140 °C (average) or 180 °C (at any single point).


Designing the building structure

The performance criteria that may need to be met, depending on the nature ofthe structural element, vary according to the circumstances, but the followingare typical of the majority of buildings.

• Load-bearing capacity is required for all structural elements including floors,beams, columns and load-bearing walls.

• Floors require insulation and integrity to protect spaces above and below thefire.

• Compartment walls require insulation and integrity to protect the adjacentspace.

• Columns require only load-bearing capacity unless they are built into anelement that requires insulation and integrity, such as a compartment wall.

• Beams require only load-bearing capacity unless they are built into a floor ora wall that requires insulation and integrity.

In some large, high or complex structures there will be a need to look beyondthe simplistic approach associated with single elements of structure such asbeams or columns. This is to make sure that there are no particular sensitiveelements of structure that could cause a disproportionate collapse during a fire.The structural/fire engineer should be able to provide an overview of the stabilityand the robustness of the structure during fire to aid this assessment. Converselythere may be elements of structure that are required during normal day-to-dayuse to reduce vibration or deflection that are redundant during a fire and thusmay not need to have fire resistance. The detail of this is beyond the scope ofBS 9999 but it will be important to establish when that boundary has beenreached as part of the design process. For further background reference can bemade to the following documents:

Introduction to the Fire Safety Engineering of Structures – IStructE

Guide to the Advanced Fire Safety Engineering of Structures – IStructE

Recommended periods of fire resistance have typically been based upon:

• the amount of combustibles (fire load density) likely within a building;• the amount of ventilation through windows and other non-fire-resisting

constructions that control the amount of oxygen available for the fire;• linking real fire performance to the standard fire tests that are used to

determine fire resistance periods for construction components (timeequivalent method);

• heat loss into compartment surfaces.



BS 9999 has coupled this method with other engineering approaches toevaluate variables and the risks associated with building height and occupancycharacteristics, thus providing a transparent method for the recommendation offire resistance periods (Ref: ‘A new approach to specifying fire resistanceperiods’, Kirby et al., Structural Engineer, October 2004). The following factorsinfluenced the recommendations for periods of fire resistance within thestandard.

• Buildings with a high potential for ventilation to outside will encountershorter fire durations.

• Sprinklers reduce the fire severity but do not necessarily extinguish the fire.• A sleeping occupancy within a building represents a greater risk compared

with occupants who are awake.• The perceived risk associated with structural failure increases with the height

of the building.

The above approach has led to the inclusion of two additional height categories,11 m and 60 m, compared with the typical guidance within Approved DocumentB. This has introduced benefit to the following buildings:

• three and four storey buildings that typically had to meet the samerecommendations as five and six storey buildings;

• 9 to 16 storey buildings that typically had to meet the samerecommendations as a building that was substantially higher.

BS 9999 includes two tables that provide recommended fire resistance periodsfor buildings; one table is based upon the engineering approach discussedabove, and the second table, which originates from Table A2 of ApprovedDocument B, is for use where recommended ventilation conditions are notachieved. Figure 16 illustrates the route necessary for determining the applicablefire resistance period.

In addition to the overall fire resistance requirements described above, there arefurther requirements and guidance on measures to prevent the spread of fireand smoke through cavities, for the fire properties of internal linings, externalwalls and roof surfaces. Also the design of ductwork systems, includingdampers, details for doors, hardware, cavity barriers, recommendations forengineering services and spread of fire between buildings are also covered in thestandard.





Determine minimum fire resistanceperiod relevant for construction component (Table 15)

Is Table 16 referenced in Table 15

Does the design meet the ventilation conditions applicable to the selected risk profile outlined inTable 17?

Yes

No Use period of minutes provided in Table 15

UseTable 16 to determine the fire resistance applicable to the selected risk profile

Yes

Refer to BS 9999: Table 25

No

Alternative

Figure 16 – Route for determining the applicable fire resistance periods

© Buro Happold

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Part of building Minimum provisions when tested to the relevant parts of BS 476 orthe relevant European standard, in minutesA)

Method of exposure

Load-bearing capacity Integrity Insulation

Structural frame,beam or column

* Not applicable Not applicable Exposed faces

Load-bearing wallelement

* Not applicable Not applicable Each side separately

FloorB)

Between a shop and aflat above

60 or *C) 60 or *C) 60 or *C) From underside

Any other floor,including compartmentfloors

* * * From underside

Roof

Any part forming anescape route

30 30 30

Any roof that performsthe function of a floor

* * * From underside

External wall

Any part less than 1 maway from any point onthe relevant boundary

* * * Each side separately

Table 15 – Minimum fire resistance performance (BS 9999: Table 24)

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Method of exposure


Any part 1 m or morefrom the relevantboundaryD)

* * 15 From inside thebuilding

Any part adjacent to anexternal escape route

30 30 No provisionE) From inside thebuilding

Compartment wall

Walls separatingoccupancies other thanoccupancies inoccupancycharacteristic A (office)

60 or *F) 60 or *F) 60 or *F) Each side separately

Any other compartmentwalls


Protected shaft,excluding any firefighting shafts

Glazed screenseparating protectedshaft from lobby orcorridor

Not applicable 30 No provisionE), G) Each side separately

Table 15 – Minimum fire resistance performance (BS 9999: Table 24) (contd)

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Any other part betweenthe shaft and aprotectedcorridor/lobby

30 30 30 Each side separately

Any other part notdescribed above


Fire-fighting shaft

Construction separatingfire-fighting shaft fromrest of building

120 120 120 From side remote fromshaft

60 60 60 From shaft side

Construction separatingfire-fighting stair, fire-fighting lift shaft andfire-fighting lobby


Enclosure

Not forming part of acompartment wall or aprotected shaft, to aprotected lobby or aprotected corridor

30 30 30E) Each side separately

In a flat, to a protectedentrance hall or aprotected landing


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Method of exposure


Subdivision of a corridor 30 30 30E) Each side separately

Fire-resistingconstruction

Enclosing communalareas in shelteredhousing


Enclosing places ofspecial fire hazard


Between storeroomsand sales area in shops


Cavity barrier Not applicable 30 15 Each side separately

DuctH) Not applicable 30 No provision From outside

Casing around adrainage systemH)

Not applicable 30 No provision From outside

Flue wallsH) Not applicable Half the period statedfor compartment wall/floor

Half the period statedfor compartment wall/floor

From outside

Fire door See Table 19 See Table 19 See Table 19

Constructionenclosing a roadway

120 120 120 From the roadway side

Table 15 – Minimum fire resistance performance (BS 9999: Table 24) (contd)

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reA) Part 21 for load-bearing elements, Part 22 for non-load-bearing elements, Part 23 for fire-protecting suspended ceilings, andPart 24 for ventilation ducts. BS 476-8 results are acceptable for items tested or assessed before 1 January 1988.B) Guidance on increasing the fire resistance of existing timber floors is given in DG 208.C) Whichever is greater.D) The guidance in BS 9999: Figure 18 and BR 187 allows such walls to contain areas which need not be fire-resisting(unprotected areas).E) Except for any limitations on glazed elements given in 31.3 of BS 9999.F) Whichever is less.G) See BS 9999: Clause 31.3.2H) BS 9999: Clause 33.

* The applicable period from Table 16 where the ventilation conditions of Table 17 are met. Refer to BS 9999: Table 25 wherethe ventilation conditions of Table 17 cannot be met.

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Risk profile Minimum periods of fire resistance, in minutesA)

Height of top occupied storey above access level

Not morethan 5 m

Not more than11 m

Not more than18 m

Not more than30 m

Not more than60 m

Morethan 60 m

A1 15 30 30 60 75 90

A2 30B) 30 60 90 120 150

A3 60 60 90 120 300 300

A4 N/A N/A N/A N/A N/A N/A

B1 30 30 30 60 60 75

B2 30 30 60 75 90 120

B3 30 45 75 105 135 180

B4 N/A N/A N/A N/A N/A N/A

CiC) 45D) 60 75 75 90 105

Ci2C) 60D) 90 105 120 N/A N/A

Cii1 or Ciii1 30 30 30 45 60 60

Cii2 or Ciii2 30 45 60 75 90 105

C3 N/A N/A N/A N/A N/A N/A

C4 N/A N/A N/A N/A N/A N/A

Table 16 – Fire resistance periods for elements of structure (based on the ventilation conditions)(BS 9999: Table 26)

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reNOTE 1 For occupancy characteristic A covering storage and car parks, and all basements, the fire resistance periods are asgiven in BS 9999: Table 25.

NOTE 2 Variation of the risk profile by the addition of sprinklers conforming to BS EN 12845 (new systems) or BS 5306-2(existing systems) can be used to reduce the fire resistance as described in BS 9999: Subclause 6.5.A) Where a product or system is not available to meet the specific classification recommended in this table, then a product orsystem should be used that has the next highest available classification category. The classification periods 75, 105 and 135 donot exist in European classification system BS EN 13501-2.B) Reduced to 15 min when ground floor area is less than 1,000 m2.C) 15 min reduction when compartment size is limited to 10 per cent of the floor area on each floor (cannot be used incombination with the reduction in footnote D).D) Reduced to 30 min for single-owner occupancy (cannot be used in combination with the reduction in footnote C).




Use Ventilation parameter

Minimum potentialarea as percentageof floor area

Height of openingA)

as a percentage ofthe compartmentheight (i.e.from floor toceiling)

A Office 5 30 to 90

A Industrial: lowhazard

2.5 30 to 80

A Industrial: highhazard

2.5 30 to 80

B Shops andcommercial

5 50 to 100

B Assembly: lowhazard

2.5 30 to 80

B Assembly:medium hazard

2.5 30 to 80

B Assembly: highhazard

2.5 30 to 80

Ci Individualresidential

10 30 to 90

Cii and Ciii Other residential 10 40 to 90

A) This is the weighted mean height (by ventilation area) of the potential openings. Ifa compartment has openings each with an area of A1, A2, A3,…An and heights of h1,h2, h3,… hn, then the total area of the openings A = A1 + A2 + A3 +… An, and theweighted mean height, h, is given by:

hA h A h A h A h

An n

�

� � � �1 1 2 2 3 3

NOTE In the calculation of the weighted mean height it is also acceptable toconsider selectively only the height(s) of the openings that achieve the minimumventilation area.

If h is the weighted mean height of all the openings and H is the height of thecompartment then h/H should be between the values given in the end column.

Table 17 – Ventilation conditions for application of Table 16(BS 9999: Table 27)



Risk profile Single storey Multi-storey

Maximum floorarea

m2

Height of topfloor

m

Maximum floorarea

m2

A1 No limit No limit No limit

A2 No limit <30 No limit

>30 Not applicable

A3A) No limit <18 14,000

18 to 30 4,000

A4 Not applicable Not applicable Not applicable

B1 No limit <30 No limit

>30 Not applicable

B2 No limit <18 8,000

No limit 4,000

B3 2,000 No limit 2,000

B4 Not applicable Not applicable Not applicable

C1 No limit No limit No limit

C2 No limit <30 No limit

C3 No limit Not applicable Not applicable

C4 Not applicable Not applicable Not applicable

A) Guidance on the maximum dimensions of compartments for risk profile has notbeen included with the standard. As the standard recommends that all buildingswith a top floor above 30 m are protected by sprinklers, it is unlikely that an A3 riskprofile will occur in buildings over this height. In the unlikely event that a space withan A3 risk profile does occur, adopting the guidance for a B3 risk profile would beappropriate.

Table 18 – Maximum dimensions of compartments (BS 9999: Table 30)



1

1

4

3

3

2

4

30 m

None of the floors in this case would need to be compartment floors, but the two storeys exceeding 2,000 m2 would need to be divided into compartments not more than 2,000 m2 by compartment walls.

NOTE The compartment walls in this example do not need to be in one vertical plane.

In a building over 30 m in height, all storeys should be separatedby compartment floors. For adviceon the special conditions in atrium buildings see Chapter 9.

a) Example of compartmentation in an unsprinklered shop

b) Compartmentation in tallbuildings

Only the floor of the ground storey need be a compartment floor if the lower basement is at a depth of not more than 10 m.

All basement storeys should be separated by compartment floors if any storey is at a depth of more than 10 m.

stnemesab peeD )d stnemesab wollahS )c

Key 1 Storey not exceeding 2,000 m2

2 Roof 3 Compartment wall 4 Storey exceeding 2,000 m2 divided by compartment wall

Figure 17 – Compartment floors (BS 9999: Figure 24)

Compartmentation

It may be necessary to restrict the spread of fire by separating one or moreareas of the building from adjacent areas and creating individual fire-protectedcompartments. This may be necessary horizontally and/or vertically and can bedependent upon several features of the building layout such as:

• to support an evacuation strategy based upon either progressive horizontalescape or escape to an area of relative safety;

• to support a phased evacuation strategy;• to separate individual floors within high-rise buildings (>30 m in height);• to separate floors within buildings with occupancy characteristic C (except

floors between one level and another within a single unit having occupancycharacteristic Ci);

• to separate basement storeys where there is a basement floor level >10 mbelow grade;

• to separate basement storeys from above ground storeys3.• to separate different risk profiles where different standards of fire resistance

or means of escape are being applied;• where compartment size on any one storey (see Figure 17) exceeds the

limitation outlined in Table 18.

Openings within fire-resisting construction (compartmentationor escape routes)

Openings within fire-resisting constructions forming compartmentation or protectingescape routes should be protected such that they do not represent a weaknessin the fire protection strategy for a building.

The provision of fire doors to protect openings within such construction shouldmeet the recommendations in Table 19. Note that all doors having a suffix ‘S’should adequately resist the passage of cold smoke (refer to BS 9999: Clause33.1.7 for further guidance).



3 Except occupancy characteristic Ci where the ground floor and basement storey immediately below ispart of the same unit (i.e. same occupancy), buildings comprising only one basement storey and twoother storeys each having a floor area �280 m2 or the ground floor is penetrated by an atrium thatmeets the recommendations of Chapter 9.

All other openings within fire resisting construction should be protected with asuitable proprietary device tested in accordance with the appropriate BritishStandard. Refer to BS 9999: Clause 33 for further guidance.

External fire spread between neighbouring buildings

The guidance given in the standard is concerned with restricting the potentialspread of fire from the building of origin to a neighbouring building. Forbuildings within 1 m of the relevant boundary, flame spread is considered theprimary fire spread mechanism. Beyond this distance, the primary fire spreadmechanism is considered to be thermal radiation.

External walls or parts of external walls within 1 m of a boundary should beconstructed to meet the appropriate period of fire resistance as recommendedby Table 15 herein with the exclusion of small unprotected areas meeting therecommendations of Figure 18.

With the exclusion of small unprotected areas meeting the recommendationsof Figure 18, the unprotected areas of external walls or parts of external walls1 m or more from a boundary should meet the recommendations of BR 187.Alternatively a fire engineering approach should be adopted. Refer to BS 9999:Clause 36.4.4 for specific alternative guidance relating to small occupancycharacteristic C buildings.

The external surfaces of walls should meet the recommendations in Figure 19.





Values in minutes

Position of door Minimum fire resistance of door in terms ofintegrity

When tested inaccordance withBS 476-22

When tested inaccordance withBS EN 1634-1

1 In a compartment wallseparating buildings

As for the wall in whichdoor is fitted, but notless than 60 min

As for the wall in whichthe door is fitted, butnot less than 60 min

2 In a compartment wall:

a if it separates a flatfroma space in common use

FD 30S E 30 Sa

b enclosing a protectedshaft forming astairway situated whollyor partly above theadjoining ground inoccupancy characteristicA (office only), B, Ci, Ciiand Ciii buildings

FD 30S E 30 Sa

c enclosing a protectedshaft forming astairway not describedin 2b)

Half the period of fireresistance of the wall inwhich it is fitted but notless than 30 min andwith suffix SC)

Half the period of fireresistance of the wallin which it is fitted butnot less than 30 minminimum and withsuffix Sa

C)

d enclosing a protectedshaft forming a lift orservice shaft

Half the period of fireresistance of the wall inwhich it is fitted but notless than 30 min

Half the period of fireresistance of the wall inwhich it is fitted but notless than 30 min

e not described in 2a),2b), 2c) or 2d)

As for the wall it isfitted in, but with suffixS if the door is used forprogressive horizontalevacuation

As for the wall it isfitted in, but add Sa

C) ifthe door is used forprogressive horizontalevacuation

3 In a compartment floor As for the floor in whichit is fitted

As for the floor in whichit is fitted

Table 19 – Provision of fire doors (BS 9999: Table 32)



Values in minutes




4 Forming part of theenclosure of:

a a protected stairway(except where describedin item 10)

FD 30S E 30 Sa

b the separation betweenupward and downwardflights of a basementstair (see Section 5)

FD 30S E 30 Sa

c lift shaft, which doesnot form a protectedshaft in 2b), 2c) or 2d)

FD 30 E 30

5 Forming part of theenclosures of:

a a protected lobbyapproach (or protectedcorridor) to a stairway,except for afire-fighting stair

FD 30S E 30 Sa

b any other protectedcorridor, or

FD 20S E 20 Sa

c a protected lobbyapproach to a lift shaft

FD 30S E 30 Sa

6 Forming part of theenclosures of:

a evacuation lifts orrefuges, except for liftlanding doors

FD 30S E 30 Sa

b evacuation lifts, wherethe door is a lift landingdoor

FD 30 E 30

7 Affording access to anexternal escape route

FD 30 E 30

Table 19 – Provision of fire doors (BS 9999: Table 32) (contd)



Values in minutes




8 Subdividing:

a corridors connectingalternative exits

FD 20S E 20 Sa

b dead-end portions ofcorridors from theremainder of the corridor

FD 20S E 20 Sa

9 Any door:

a within a cavity barrier FD 30 E 30

b forming part ofthe enclosure to acommunal area insheltered housing

FD 30S E 20 Sa

10 Any door:

a forming part of theenclosure to a protectedentrance hall or protectedlanding in a flat

FD 20 E 20

b within any other fire-resisting construction indwelling accommodationnot described elsewherein this table

FD 20 E 20

NOTE 1 For fire-fighting shafts, see BS 9999: Clause 21.2.

NOTE 2 The national classifications do not automatically equate with the equivalentclassifications in the final column; therefore products cannot typically assume aEuropean class unless they have been tested accordingly.A) Fire doors are designated by reference to their recommended performance (inminutes) for integrity only, and whether they need to retard the passage of smoke atambient temperature. The need to include insulation as part of the specification isdependent on the function of the door. For example, reference FD 60 is to a doorthat should achieve not less than 60 min integrity when tested in accordance withBS 476-22 or BS EN 1634-1.




1

1

3

2

1.5 m

4 m

1.5 m

4 m

..........

4 m

1

Key 1 Unrestricted

Represents an unprotected area of not more than 1 m2 which may consist of two or more smaller areas within an area of 1,000 mm × 1,000 mm

2 External wall of shaft that is enclosed by a minimum of 60 min fire resistance from the accommodation side

3 Compartment boundaries

Represents an area of not more than 0.1m2

Figure 18 – Small unprotected areas allowable without calculation(BS 9999: Figure 41)

B) Or with BS 476-8, in respect of items tested or assessed prior to 1 January 1988.C) Fire doors having suffix S should either:

• Have a leakage rate not exceeding 3 m3/h per metre, when tested in accordancewith BS 476-31.1 with the threshold taped and subjected to a pressure of 25Pa; or

• Meet the classification requirement of Sa when tested in accordance with BS EN 1634-3.




<1 m

1

>1 m

1

>1 m>1 m

23

a) Any building c) Assembly or recreation buildingof more than one storey

Key 1 Building height <18 m 2 Up to 10 m above ground level 3 Up to 10 m above a roof or any part of the building to which the public has access 4 Building height 18 m or more 5 Portion of building more than 18 m above ground level 6 Portion of building up to 18 m above ground level

Relevant boundary No provision in respect of the boundaries indicated Class 0 (national class) or class B-S3, d2 or better (European class). Profiled or

flat steel sheet at least 0.5 mm thick with an organic coating of no more than 0.2 mm thickness is also acceptable.

Index (I) not more than 20 (national class) or class C-s3, d2 or better (European class). Timber cladding at least 9 mm thick is also acceptable. (The index I relates to tests specified in BS 476-6.)

<1 m

<1 m

4

>1 m >1 m

5

46

gnidliub ynA )e gnidliub ynA )d

NOTE 1 The national classifications do not automatically equate to the equivalent European classifications; therefore products cannot typically assume a European class unless they have been tested accordingly.

NOTE 2 When a classification includes ‘s3, d2’, this means that there is no limit set for smoke production and/or flaming droplets/particles.

b) Any building other than c)

Figure 19 – Provisions for external surfaces of walls(BS 9999: Figure 45)

9. Recommendations for atria

Key points

• Design solutions are not applicable to the following:c buildings intended to confine occupants;c theatres, cinemas and similar venues (see Chapter 10);c shopping malls (see Chapter 11);c small premises and buildings with occupancy characteristics A and B

containing an atrium uniting only two storeys and designed forsimultaneous evacuation.

• It is not necessary to separate any below-ground and above-groundsections of an atrium.

• Phased evacuation should be used only where occupied floors areseparated from atria by imperforate construction (smoke and/or fireresisting); simultaneous evacuation should be used in all other cases.

• Escape routes should not need to pass within 4.5 m of the atrium edgeunless occupants are protected by either imperforate construction (smokeand/or fire resisting) or a smoke control system.

• Smoke-resisting construction should be used only where smoketemperatures are controlled by sprinklers and/or smoke control systems.

• Control of fire loads on the atrium base, without sprinklers, can beachieved by limiting fire load areas to �10 m2 and separating them by atleast 4 m from adjacent fire loads.

• A smoke control system should be provided in buildings with occupancycharacteristic A where phased evacuation is adopted or the heightexceeds 30 m, and in all buildings with occupancy characteristic B. Thetype of smoke control system is dependent upon the method ofseparation between the atria and the adjoining floor areas.

• Smoke clearance for fire-fighting should be provided in all atria notprovided with a smoke control system and based upon the following:c natural vents within atria �18 m, equivalent to 10 per cent of the atrium

plan area;c mechanically ventilated to six air changes per hour in atria of any height

where the building is not sprinkler protected, equivalent to the volumeof the atrium and the largest floor open to the atrium;


c mechanically ventilated to four air changes per hour in atria of anyheight where the building is sprinkler protected, equivalent to thevolume of the atrium and the largest floor open to the atrium.

• For sprinkler-protected atrium buildings, external fire spread assessments canassume that the building is equivalent to a fully compartmented non-atriumbuilding. All other atrium buildings should consider the atrium and anyadjoining floors not fire separated from the atrium as one compartment.

• If an atrium design cannot meet the recommendations of BS 9999:Annexes B and C, then it will be necessary to adopt a fire engineeredalternative approach.

Background

The inclusion of atria within buildings results in the connection of multiplestoreys such that smoke from a fire on any storey, or in the atrium base, couldpotentially spread via the atria and present a hazard to occupants that areremote from the storey of fire origin. The majority of smoke from a fire on astorey open to an atrium will spread directly into the atrium; the developmentof the smoke layer on the storey of fire origin is reduced leading to an increasein the time available for escape on the storey of fire origin. As the smoke risesthrough the atrium, it entrains large quantities of clean ambient air increasingthe volume but also diluting the concentration of smoke particles and reducingthe temperature of the smoke. This can also lead to the build-up of smoke onupper storeys open to the atrium, and although this smoke will be significantlymore dilute than on the storey of fire origin it may necessitate immediateevacuation of those upper storeys or partial enclosure to provide additional timeavailable for escape (this is highlighted in Figure 20). Consequently, therecommendations within BS 9999 for the fire safety design of atria dependupon the type of enclosure provided (if any), the height of the atria, the methodof evacuation adopted and the occupancy characteristics.

The standard does not at this time use the risk profile in its entirety but it doestake full advantage of the occupancy characteristics to vary the recommendations.A wide range of solutions (exemplars) are outlined in BS 9999: Annex C andtheir use is informed by a set of decision trees providing a route map throughthe selection process. It should be recognized that the solutions documentedare not exhaustive, may not be appropriate to all buildings and that alternativesolutions may exist by which an equivalent level of fire safety can be achieved.


Recommendations for atria

Such approaches are beyond the scope of BS 9999 and would require adoptionof a fire engineering approach.

Equally it is not possible to replicate all of the exemplars from the standard inthis handbook. However, exemplars for the most common atria solutions arereproduced in Figures 21 to 24. Further detailed guidance can be found inBS 9999: Annexes B and C.

Escape routes

Escapes routes typically coincide with circulation routes, but in a buildingcontaining atria this may not be appropriate if travel close to the edge of anopen atrium is necessary.

The design of the means of escape should follow the principles of the equivalentnon-atrium building (see Chapter 6). However, where accommodation is opento an atrium or not separated by smoke-retarding construction, storey exitsshould be sited away from the atrium so that escape routes do not pass within4.5 m of the atrium edge. Further guidance on acceptable escape along balconiesis provided within BS 9999: Clause B.4.3, and typically necessitates the protectionof the balcony from the effects of heat and smoke unless an alternative escaperoute is available.



Figure 20 – Example of smoke plume movement



3

2

4

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

1 1

AFD18m

6

3

4

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

AFD/A SE

1 1

AFD

18 m

Key 1 Smoke clearance system 2 Smoke-retarding enclosure but not fire-resisting 3 Open or enclosed 4 Atrium base: use and contents comparable with that adjoining the atrium 5 Make-up air 6 Smoke reservoir AFD Automatic fire detection connected to the building fire alarm system AFD/A Automatic fire detection within the atrium and associated floor areas and alarm throughout the building SE Simultaneous evacuation

5 5

5 5

Figure 21 – Occupancy characteristic A (awake and familiar) – 18 m orless in height, open or closed, simultaneous evacuation (BS 9999:

Figure C.8 – Exemplar 2)



2

3

1 1

AFD18 m

AFD/VA SE

3

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

Key 1 Smoke exhaust system 2 Atrium base: controlled fire load 3 Make-up air AFD Automatic fire detection connected to the building fire alarm system AFD/VA L2 automatic fire detection within the atrium and associated floor areas and voice alarm throughout the building SE Simultaneous evacuation

Automatic sprinkler protection

Figure 22 – Occupancy characteristic B (awake and unfamiliar) – 18 mor less in height, open, simultaneous evacuation

(BS 9999: Figure C.24 – Exemplar 12)



44

2

3

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

AFD/VA SE

1 1

AFD18 m

Key 1 Smoke clearance system 2 Enclosed fire-resisting (30 min integrity) and smoke-retarding construction 3 Atrium base: controlled fire load 4 Make-up air AFD Automatic fire detection connected to the building fire alarm system AFD/VA L2 automatic fire detection within the atrium and associated floor areas and voice alarm throughout the building SE Simultaneous evacuation

Figure 23 – Occupancy characteristic B (awake and unfamiliar) – 18 mor less in height, enclosed, fire-resisting, simultaneous evacuation




66

5

3

4

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

L1AFD/VA

1 1

AFD

2 2

Key 1 Smoke clearance system 2 Protected escape route directly from accommodation independent of atrium 3 30 min fire-resisting and smoke-retarding construction 4 Unlimited height 5 Atrium base: controlled fire load 6 Make-up air AFD Automatic fire detection connected to the building fire alarm system L1AFD/VA L1 automatic fire detection A) and voice alarm throughout the building

A) Automatic fire detection conforming to the L1 standard as specified in BS 5839-1:2002+A2:2008.

Figure 24 – Occupancy characteristic Ciii (asleep and unfamiliar) –Short-term occupancy, protected escape route, any height


Smoke and heat control systems

Smoke control is an integral part of the fire safety design solutions (exemplars)outlined in BS 9999: Annex C and uses a combination of passive (smoke-retarding/fire resisting construction) and active measures. Where active smokecontrol is necessary and requires engineering calculation, the methodologyshould be in accordance with recognized documents, such as PD 7974: Part 2,BS 7346: Part 4 and BR 368.




10. Recommendations for theatres,cinemas and similar venues

Key points

• Foyers serving several auditoria (theatres, cinemas, etc.) should be enclosedby fire resisting construction, and the foyer should be approached viaprotected lobbies.

• Transformer rooms, boiler rooms and other similar perceived risk areas shouldnot have openings located in close proximity to exits from the building.

• Within rowed seating the width between the back of a seat and the mostforward projection of the seat behind (seatway width) should not be lessthan 300 mm and should be constant throughout the length of the row(see Figure 25).

• Seating within closely seated layouts should be designed and constructedsuch that they are resistant to ignition sources 0, 1 and 5 when tested inaccordance with BS 5852: 2006.

• The slope of any tiered seating should not exceed an angle of 35 degreesto the horizontal.

• Travel distances within tiered seating should not exceed 15 m whereescape is available in one direction only and 32 m where escape isavailable in more than one direction.

• Gangways serving more than 60 persons should have a minimum widthof 1,100 mm. Those serving fewer than 60 persons can be reduced to900 mm.

• Temporary seating for between 50 persons and 250 persons should besecured together in lengths of at least four seats. Temporary seating formore than 250 persons should be fixed to the floor, although this fixingcan be at the end of rows where all seats are secured together.

• Where a proscenium wall is provided (separated stages) it should beconstructed of non-combustible material achieving a 60 minute fireresistance period. The associated safety curtain should be of non-combustiblematerial and should withstand the effects of fire for the duration of theevacuation.

• Protected lobbies should be provided between the stage basement andthe orchestra pit, and between the stage and the following areas:

c dressing room corridor(s);c final exit(s) to open air; andc the auditorium when a pass door is provided in a proscenium wall.

• At least one escape route from the dressing rooms should be independentof the stage.

• Separated stages (stages with a proscenium wall and safety curtain)should be automatically ventilated at a temperature not exceeding 74 °C,by sprinkler activation when provided, and additionally have a manualopening facility.

• Open stages should be ventilated to keep the auditorium clear of smokeduring means of escape and should be equivalent to a total aerodynamicarea of at least 10 per cent of the stage area.

Background

In venues with auditoria (theatres, cinemas, etc.), escape routes should bedesigned so that in the event of a fire occupants are able to evacuate the wholebuilding. To this end, the design recommendations contained within BS 9999:Annex D may be more onerous than that required to meet the BuildingRegulations.

Additional guidance in the design of such venues can be found within theTechnical Standards for Places of Entertainment produced by the Association ofBritish Theatre Technicians, the District Surveyors Association and the Institute ofLicensing.

Seating and exit layouts

Limitations on travel distance control the maximum spacing of exits, but theactual location may be driven by the seating layout and the provision for spacesfor wheelchair users and ambulant disabled people (see also BS 8300).

Where gangways are provided at each end of seating rows and generous seatwaywidths are provided, the number of seats in a row is relatively unimportantprovided that travel distances are within acceptable limits. In other instances it isnecessary to limit the number of persons, for example to account for reducedmovement speeds due to narrow seatway widths. Figure 25 outlines the maximumrecommended number of seats within a row.


Recommendations for theatres, cinemas and similar venues

Exits located at the rear of a seating tier may reduce overall travel distance,although this may be one of the first areas to be directly affected by smokefrom a fire in the activity area. Therefore some form of smoke control may benecessary to prevent early smoke logging of such exit routes. The escape ofoccupants towards an activity area is acceptable providing that the occupantswould not be directly affected by a fire during the evacuation period.

Furnishings, fabrics and decorative features

Furnishings, fabrics and decorative features (including drapes and artificialfoliage) should be of materials that do not significantly increase the combustible



Seatway width (mm)

1 1 1 1 1

(1 = Seatway) Gangway on one side

Gangway on two sides

41 7 423 ot 003 61 8 943 ot 523 81 9 473 ot 053 02 01 993 ot 573 22 11 424 ot 004 42 21 944 ot 524 62 21 474 ot 054 82 21 994 ot 574

m 23 yb detimiL 21 erom ro 005travel distance as escape is availablein more than one direction

Maximum number of seats in a row

Figure 25 – Number of seats in a row (BS 9999: Figure D.1 andTable D.1)

materials within the building and be suitably robust that washing is notdetrimental to their performance. Therefore such materials should either benon-combustible or should be of a type B classification when tested in accordancewith BS 5867 Part 2:2008 (after being subjected to the appropriate wetting orcleansing procedure described in BS 5651). However, only non-combustiblematerials should be provided within enclosed escape routes (excluding foyers).In addition, drapes should not be provided in front of exit doors or acrossescape routes.

Stage areas

The stage area comprises the stage and its ancillary areas, such as prop/scenerystores and quick-change rooms.

There might be a high fire loading on the stage, particularly because of thequantities of scenery and curtains involved. The risk of fire can be increasedbecause of temporary props, furniture and temporary lighting equipment. However,the stage area is likely to have close supervision whenever the public is present.

A proscenium wall, safety curtain and smoke ventilation above the stage areacan protect occupants from the effects of a fire on the stage for the evacuationperiod. However, not all venues can readily separate the stage from spectators, i.e.open-stage configurations. Where a stage does not have a safety curtain, theapproving authority may limit the amount and type of scenery used. There may bea need for higher standards of flame retarding, limiting the materials available forthe construction of scenery, and subsequently increasing running costs. Theapproving authority should be consulted at an early stage where an open stageconfiguration is proposed and a fire engineering approach may be required.

Spaces that are ancillary to the stage are areas of intense activity during a stagepresentation and may be highly loaded with combustibles. Therefore, spacessuch as dressing rooms and scene docks should be enclosed in fire-resistingconstruction, and any openings should be suitably protected fire-rated assemblies.In addition, scene docks should be provided with manually operated smokeventilation.

Grid and fly galleries provide additional facilities for scenery and lighting. Theseareas can be particularly hazardous in the event of a fire on the stage. Access istypically via fixed ladders, although in a fire situation access to an alternativemeans of escape is recommended.




11. Recommendations for shoppingcomplexes

Key points

• The recommendations are typically appropriate to new shopping complexes,but guidance appropriate for existing and uncovered malls, and smallarcades, is also provided.

• Automatic sprinkler protection should be provided throughout all areas ofbuildings that are connected to covered malls unless such buildings arefully separated and have escape routes that are fully independent of themall.

• Covered mall complexes should be provided with a smoke control systemdesigned in accordance with BS 7346 Part 4 and BRE guidance documentsBR 186 and BR 368. Uncovered mall complexes do not necessitate smokecontrol.

• Other non-public areas may also require some form of smoke control, i.e.high-risk areas within basements.

• Covered malls with units on both sides of the mall should have a minimumeffective width of 6 m to provide adequate escape and minimumseparation between unit demises across the mall.

• Uncovered malls with units on both sides of the mall should have aminimum separation of 5 m between unit demises across the mall.

• The minimum exit width provided from all malls with a width up to 8 mshould be based upon an occupant load factor of one person for every0.75 m2 (or 1.0 m2 for seated areas) of mall area. For malls with a widthgreater than 8m then an occupant load factor of one person for every 2.0m2

should be used for that part of the mall width over 8 m. This recognizesthat wider malls will be less crowded than similar narrower malls.

• Exits from a mall should not discharge into car parks, but exits from aretail unit may do so where the car park is fire separated from the mallcomplex, or the car park is in open air, or is accessed via an open-airbridge link.

• Escape routes through service areas, car parks, unloading docks or similarareas are acceptable providing such routes are clearly defined (guardedwith protective barriers where necessary) and have a minimum width of 2m.

• All service corridors serving units within mall complexes should besubdivided with a self-closing fire door, or be provided with protectedlobbies between the unit(s) and corridor, or be protected by anappropriate smoke control system.

• Service corridors are acceptable to serve as an alternative means of escapefor units having an occupant load of �300 persons providing that thewidth provided incorporates an additional 0.5 m to that required by thelargest unit served and the overall width of the corridor is �2.0m but �3.0m.

• If a service corridor serves a unit as an alternative escape route it shouldlead directly to a storey exit, and if it is greater >45 m it should have astorey exit at each end.

• A fire control centre for fire service use should be provided within allshopping complexes.

• A wet fire main system can be used to provide adequate access for fire-fighting operations within a complex that has a deep plan provided thatthe route taken to the fire main outlet point is protected by fire-resistingconstruction.

• Buildings within uncovered mall complexes do not necessitate the samelevel of fire protection measures compared with a covered mall, althoughconsideration should be given to the future enclosure of the uncoveredmall(s) and the additional measures that may be necessary, i.e. sprinklerprotection, separation between buildings, etc.

• Small shopping developments, i.e. small arcades, may not meet theminimum recommendations for new-build covered shopping malls andtherefore guidance within BS 9999 for a similar uncompartmented retailunit should be followed or a fire engineering approach should be adoptedwhere this is not appropriate.

Background

Many early shopping complexes were designed with single-level access and withthe public circulation spaces open to external air. Over time the trend has beento provide cover, of various degrees, to the public. This has led to a range ofshopping experiences from covering existing small shopping arcades to purposebuilt, multi-level, fully enclosed, shopping complexes. The latter typicallyincorporates a complex interaction of atria and vertical circulation routes thatconnect several levels within a public mall, and escaping occupants are expectedto escape via these malls.


Recommendations for shopping complexes

Consequently, modern shopping mall complexes provide a different set of firesafety issues from those that are common to an individual retail unit. BS 9999:Annex E provides guidance on how to tackle these issues.

Means of escape and motivation to escape

Motivation to escape is important. Research into several major fatal fires andevacuations suggests that in large internal spaces people in a crowd havedifficulty in recognizing any immediate threat from a fire elsewhere in thebuilding. People are also likely to underestimate how quickly a fire can spread.In a fire disaster, the uncertainty of the situation in its early stages is usuallycompounded by a serious delay in warning the public in time for them to startto evacuate and to reach safety. To overcome these problems it is necessary toprovide a package of related fire precautions measures, complementary stafftraining and evacuation management procedures, and to introduce appropriatemeans of escape criteria, aimed at achieving an acceptable level of means ofescape conditions in these areas, taking into account the potential risk profile.

Smoke control

In a town centre high street, a fire in a retail unit will probably threaten only theoccupants in that building. However, a covered shopping complex has individualunits opening onto a covered mall, potentially incorporating atria, and smokefrom a fire in any unit could spread rapidly via the mall system. Therefore a firein an individual unit may present a hazard to occupants that are remote fromthe unit of fire origin. This design issue coupled with the fact that such complexescan be very densely populated at peak times requires that a greater time isprovided for occupant evacuation through the use of smoke control. Smokecontrol is therefore an integral part of design in covered shopping complexesand should be designed in accordance with BS 7346-4 and BRE Reports BR 186and BR 368.

Fire protection

In addition to the smoke control highlighted above, other fire protectionmeasures will be necessary within covered shopping complexes in order tosupport the need for the control of smoke and fire spread. Such measureswould include the provision of sprinkler protection and an automatic fire alarm



system throughout a covered shopping complex. These systems also complementthe fire control centre and other facilities necessary for fire-fighting operationswithin covered complexes.

Uncovered shopping complexes

With respect to fire safety design, the majority of uncovered complexes may besimilar to a high street shopping district. Therefore some of the fire protectionmeasures recommended for covered complexes, in particular smoke control andsprinkler protection, would not be necessary. However, during the design stageof a project, consideration should be given to the possibility of future proofingthe complex for being covered at a later date.

Small shopping developments or arcades

Small shopping developments, such as small covered arcades, may not readilymeet the recommendations aimed at purpose built covered shopping malls andtherefore guidance within Annex E of the standard may be unduly restrictive.Therefore such developments, whether new build or formed by the covering ofan existing arcade, should follow the guidance within the standard for a similaruncompartmented retail building. Where neither this approach nor Annex E issuitable, then a fire engineering approach will be required.

Covering existing streets

There are occasions when existing large streets are covered, sometimes at ahigh or low level. The mix of sprinklered and unsprinklered shops associatedwith a wide building represents a more considerable design challenge. Unlesssignificant changes can be made to achieve compliance with the standard, theresolution is beyond the scope of BS 9999.



12. Process plant and outdoor structures

Key points

• Process plant buildings should generally be designed in accordance withthe section of the standard ‘Designing means of escape’, althoughdepartures from this guidance for escape widths and vertical escapecomponents may be acceptable, i.e. a ladder, where rapid smoke loggingis unlikely.

• Escape routes within weather housed, weather protected or external plantcan be designed on the basis of the maximum travel distancesrecommended in Table 20.

• The horizontal components of alternative escape routes within weatherhoused and external plant should be at least 90° apart. Verticalcomponents of escape routes within weather-housed and external plantshould either be at least 20 m apart or descend at opposite extremities ofthe structure.

Background

It is recognized that the general recommendations of the standard for certaincomponents of means of escape may be unduly restrictive on buildings that areconstructed solely for the housing of process and storage plant, primarilybecause of the characteristically low occupancy and familiarity with the premises.

Within process plant buildings there is a potential for both rapid escalation of afire and rapid smoke logging, and therefore the general recommendations ofthe standard should be followed for means of escape design. A relaxation onthe minimum width of exit routes and the use of ladders for vertical escape areallowable in buildings that pose a reduced threat of rapid smoke loggingbecause of the nature of the process or their design. However, travel distancesare not relaxed as the heat radiation associated with a rapid growing fire willcontinue to represent the greatest hazard to escaping occupants.

The sole purpose of weather housed buildings is to enclose plant from theexternal environment. Such buildings are typically large enclosures withpedestrian routes provided on the basis of required maintenance access to the


plant inside and they are likely to be at multiple levels. Therefore increased traveldistances and unenclosed vertical escape components are acceptable providedthat adequate escape routes will remain unaffected during the early stagesof a fire. These overall travel distances would include any unenclosed verticalcomponents. External escape routes with a reduced level of fire resistance mayprovide an adequate alternative where an appropriate level of resistance to heatand smoke is provided.

Weather protected plant is essentially plant that has only partial enclosure, i.e.incorporates louvers, ridge vents, etc. Therefore smoke logging is less likelycompared with weather-housed plant, and the risk posed to escaping occupantsis similar to those associated with external plant.


Process plant and outdoor structures

Situation Travel distance

m

Two-way travel One-way travel

Weather-housed plant

Risk profile A1 100 20



Risk profile A4 Not applicable Not applicable

External plant/weather-protected plant

Normal fire hazard outdoor zone 200A) 25B)

High fire hazard outdoor zoneC)

Frequently visited 100A) 13

Not frequently visited 200A) 25

A) Plus an additional 50 m at ground level where the direction of travel is substantiallyunrestricted.B) 100 m from the top of a storage tank or silo, provided that a person is not requiredto cross the top of more than one other tank to reach a route leading to groundlevel.C) Such areas are outside the scope of this British Standard unless a sprinkler systemor another appropriate fire suppression system is installed to reduce the risk profile.

Table 20 – Maximum travel distances for weather-housed, weather-protected or external plant (BS 9999: Table F.1)

External plant has minimal potential for smoke logging, although the heatradiation associated with a rapidly growing fire will continue to represent ahazard to escaping occupants. A minimum of two escape routes should beprovided from any part of the external plant area and they should be separatedsuch that they are unlikely to be simultaneously compromised during the earlystages of a fire. The overall travel distance should be measured from anyaccessible point to a point at adjacent ground level outside the confines of theplant or structure surrounding it.

The principles outlined in Chapter 6 for altering travel distances using additionalfire protection measures can be applied to the distances stated above forweather-housed plant.


Process plant and outdoor structures

13. Worked example – two storey retail unit

The example clothing retail unit is a stand-alone building independent of anyconnections to other buildings. It has two floors, the ground floor and firstfloor, which are interconnected by a void with escalators used for verticaltransportation. All escape from the first floor is independent of ground floorescape.

The floor to ceiling height on both levels is approximately 4.5 m (approximately5 m floor to floor), and the gross floor area of both levels is 2,000 m2.

An automatic alarm system incorporating automatic smoke detection will beprovided throughout the building, including the retail sales floor.

The façade is constructed from floor to ceiling glazing.

Step 1: Establish the risk profiles within the building (referto Tables 3 and 4)

The risk profile of the retail unit is determined by a combination of the likely firegrowth within the space and the occupant characteristics. From the risk profileof a building, the minimum fire protection measures, means of escape layout(including stair widths, door widths, travel distance, etc.) and constructionrecommendations can be determined.

Occupant characteristics

Occupants within the retail unit will be awake but may be unfamiliar with thespace. Therefore the occupant risk category can be defined as ‘B’ – ‘Occupantswho are awake and unfamiliar with the building’.

Fire growth

The fire load within the retail unit will be consistent with that expected within aclothing retail unit, i.e. racks throughout the sales floor comprising clothing,and can be approximated to a category ‘3’ – ‘fast’ fire growth.


Step 2: Identify the minimum management levelrecommended for the building (refer to Table 6)

Having determined the risk profiles for each space within the building it is easyto identify the minimum recommended management level for each risk profile.Therefore a level 1 (the highest) management level is expected throughout thebuilding due to the B3 risk profile.

Step 3: Identify the minimum fire protection featuresrecommended for the building (refer to Table 6)

The means of escape provisions recommended for a space with a particular riskprofile are based upon that space having a minimum package of fire protection.For the example retail unit, risk profile ‘B3’, the minimum package is as follows:

• L2 automatic fire detection and alarm system; and• emergency lighting on all escape routes (including external routes).

Step 4: Identify the per cent variations allowable in meansof escape components (refer to Table 8)

After the identification of the minimum fire protection measures, it is possible toidentify whether any per cent variations are allowable within the building. It ispossible to introduce variations to components associated with means of escape,i.e. travel distances and width of exits and stairs, where;

• floor to ceiling heights are greater than 3 m; and/or• automatic fire detection and alarm is not recommended within the room as a

minimum within the standard for the selected risk profile but will be providedin this case.

As identified within Step 3 above, the example retail unit does necessitateautomatic fire detection and alarm as a minimum to comply with the standard.However, this is only to an L2 standard, which does not require smoke detectionon the retail sales floor; therefore a 15 per cent variation associated with thisfire protection feature is allowable (BS 9999: Clause 19.2).

In addition, the example retail unit does incorporate floor to ceiling heights of4.5 m, and therefore a 10 per cent variation associated with this is allowable(variation for floor to ceiling heights of between 4 m and 5 m).


Worked example – two storey retail unit

Consequently, the travel distances can be extended and widths of exits andstairs can be reduced by up to the sum of the per cent variations identifiedabove, 25 per cent (subject to overriding maxima and minima identified withinBS 9999). Note that for ease of calculation purposes the per cent variations havebeen added; however, aggregation is allowable within the standard (refer to theexample in BS 9999: Clause 19.1 for further details).

Step 5: Determine the dimensions applicable to means ofescape components (refer to Tables 9, 10, 11 and Table 12)

Travel distances

On the basis of the risk profile of ‘B3’ identified in Step 1, Table 21 highlightsthe calculated travel distance after the 25 per cent variation (identified in Step 4)has been applied to risk profile B3.

However, these distances must be checked against Table 9, which outlines anoverall limit on travel distances. By referring to Table 9 it can be seen that theupper limit for risk profile B3 is not exceeded.

Horizontal exit widths

On the basis of the risk profile of ‘B3’ identified in Step 1, Table 22 highlightsthe calculated width per person after the 25 per cent variation (identified inStep 4) has been applied to risk profile B3.

However, these widths must be checked against Table 10, which outlines anoverall limit on exit width per person. From referring to Table 10 it can be seenthat the lower limit of 5.3 mm per person for risk profile B3 is exceeded andtherefore the calculated exit width of 4.5 mm per person is not acceptable andmust be increased to the limit of 5.3 mm per person.

Vertical exit widths

On the basis of stairs serving one storey and a risk profile of ‘B3’, the calculatedstair width per person is shown in Table 23 (including the 25 per cent variationwhere identified as applicable in Step 4).



Variations in stair widths are limited to a maximum of 25 per cent (BS 9999: Clause19.4.4). As the variation identified in Step 4 is 25 per cent, the calculated stair widthper person stated in Table 23 should be appropriate; however, the minimum widthper person recommended for horizontal exits is 5.3mm per person and thereforethe calculated exit width of 5.25mm per person must be increased to 5.3mm perperson to ensure that the escape stair is not narrower than the storey exit.

Step 6: Determine the minimum fire resistance period forconstruction components (refer to Tables 15, 16 and 17)

Table 15 illustrates the minimum fire resistance period recommended for thevarious construction components throughout a building. Where the number (ofminutes) is not provided or applicable, it makes reference to Table 16. Table 16



Risk profile Minimum width per personwith minimum fireprotection measures

Calculated width per person(with identified 25 per centvariation where applicable)

B3 6.0 mm per person 4.5 mm per person

Table 22 – Calculated horizontal exit width per person




Table 23 – Calculated vertical exit width per person

Risk profile Maximum travel distancewhen minimum fireprotection measures areprovided

Calculated travel distance(with identified 25 per centvariation where applicable)

Two-waytravel

One-waytravel

Two-waytravel

One-waytravel

B3 40 m 16 m 50 m 20 m

Table 21 – Calculated travel distances

can be used only where the ventilation conditions of Table 17 have been met,otherwise reference should be made to the British Standard. For the purpose ofthis example it is assumed that the ventilation conditions of Table 17 can be metfor risk profile B3.

On the basis of risk profile ‘B3’ within a building having a top floor not morethan 5 m above ground, Table 16 would recommend a minimum 30 minuteperiod of fire resistance.

Step 7: Determine the maximum compartment dimensions(refer to Table 18)

On the basis of risk profile B3 within a building having a top floor not morethan 5 m above ground, Table 18 recommends a 2,000 m2 limit be placed onthe maximum compartment area of a storey.

As the gross floor area of each storey is not more than 2,000 m2, there is nocompartment floor area limitation that would need to be incorporated withinthe example building.

As the example retail unit does not include a basement and does not have afloor more than 30 m (BS 9999: Clause 32.4.2) above ground, then there are noadditional compartmentation recommendations. Subsequently, as the guidancein BS 9999 Annex B for atria applies only when compartmentation is breached(BS 9999: Clause 32.4.1.1) the opening within the first floor for the escalatorsdoes not require any further fire protection measures.



14. Worked example – high-rise officebuilding

The example high-rise office building is a stand-alone building independent of anyconnections to other buildings. The topmost occupied floor is 45m above ground.

The floor to ceiling height on all levels is approximately 2.6 m, and the layout oneach floor will be predominantly open plan.

An automatic alarm system incorporating smoke detection will be providedthroughout the building, including the office floor areas.

As the building is over 30 m, the building will be protected throughout with anautomatic sprinkler system and will adopt a phased evacuation strategy.

The façade is constructed from floor to ceiling glazing.


The risk profile of the office building is determined by a combination of thelikely fire growth within the space and the occupant characteristics. From therisk profile of a building, the minimum fire protection measures, means ofescape layout (including stair widths, door widths, travel distance, etc.) andconstruction recommendations can be determined.


Occupants within the office building will be awake, and will be familiar with thespace. Therefore the occupant risk category can be defined as ‘A’ – ‘Occupantswho are awake and familiar with the building’.

Fire growth

The fire load within the office building can be approximated to a category ‘2’ –‘medium’ fire growth. However, the building is protected throughout with anautomatic sprinkler system and therefore in accordance with BS 9999: Clause


6.5 the fire growth rate can be reduced by one level, i.e. from category ‘2’ –‘medium’ to category ‘1’ – ‘slow’. Consequently, the risk profile has beendetermined as ‘A1’.


Having determined the risk profile for the office building, it is easy to identifythe minimum recommended management level for the building. Therefore alevel 3 (the lowest) management level is expected throughout the building dueto the A1 risk profile. It should be borne in mind that a level 3 managementsystem may not meet the requirements placed on the occupiers, owners orother responsible persons under current UK legislation, i.e. the RegulatoryReform (Fire Safety) Order in England and Wales.

Step 3: Identify the minimum fire protection featuresrecommended for the building (refer to Table 6)

The means of escape provisions recommended for a space with a particularrisk profile are based upon that space having a minimum package of fireprotection. For the example office building, risk profile ‘A1’, the minimumpackage is as follows:

• manual detection and alarm system; and• emergency lighting as per Table 6.


After the identification of the minimum fire protection measures, it is possibleto identify whether any per cent variations are allowable within the building. Itis possible to introduce variations to components associated with means ofescape, i.e. travel distances and width of exits and stairs, where:


minimum within the standard for the selected risk profile and will beprovided within the building.


Worked example – high-rise office building

As identified within Step 3 above, the example office building does notnecessitate automatic fire detection and alarm as a minimum to comply withthe standard, therefore a 15 per cent variation associated with this fireprotection feature is allowable (BS 9999: Clause 19.2).

The example office building does not incorporate floor to ceiling heights greater than3 m and therefore a per cent variation associated with this is not allowable.

Consequently, the travel distances can be extended and widths of exits andstairs can be reduced by up to 15 per cent (subject to overriding maxima andminima identified within BS 9999).

Step 5: Determine the dimensions applicable to means ofescape components (refer to Tables 9, 10, 11 and 12)

Travel distances

On the basis of a risk profile of ‘A1’ identified in Step 1, Table 24 illustratesthecalculated travel distance after the 15 per cent variation (identified in Step 4)has been applied to risk profile A1.

However, these distances must be checked against Table 9, which outlines anoverall limit on travel distances. From referring to Table 9 it can be seen that theupper limit is not exceeded for risk profile A1.


On the basis of a risk profile of ‘A1’ identified in Step 1, Table 25 illustrates thecalculated width per person after the 15 per cent variation (identified in Step 4)has been applied to risk profile A1.

However, these widths must be checked against Table 10, which outlines anoverall limit on exit width per person. From referring to Table 10 it can be seenthat the lower limit for risk profile A1 is not exceeded and therefore thecalculated exit width per person is allowable.

Vertical exit widths

The example office building will adopt a phased evacuation strategy andtherefore in accordance with BS 9999: Clause 18.4.3 the vertical exit widths



should be sized based upon serving the maximum occupancy of any twocontiguous floors.

On the basis of stairs serving two storeys and a risk profile of ‘A1’, thecalculated stair width per person is shown in Table 26 (including the 15 per centvariation where identified as applicable in Step 4).

Variations in stair widths are limited to a maximum of 25 per cent (BS 9999:Clause 19.4.4). As the variation identified in Step 4 is 15 per cent, the calculatedstair width per person stated in Table 26 is allowable.





A1 3.4 mm per person 2.89 mm per person






Risk profile Maximum travel distancewhen minimum fire protectionmeasures are provided


Two-waytravel

One-waytravel

Two-waytravel

One-waytravel

A1 65 m 26 m 74.75 m 29.9 m



Table 15 highlights the minimum fire resistance period recommended for thevarious construction components throughout a building. Where the number (ofminutes) is not provided or applicable, it makes reference to Table 16. Table 16can be used only where the ventilation conditions of Table 17 have been met,otherwise reference should be made to the British Standard. For the purpose ofthis example, it is assumed that the ventilation conditions of Table 17 can bemet for risk profile A1.

On the basis of risk profile ‘A1’ within a building having a top floor not morethan 60 m above the ground, Table 16 would recommend a minimum 75minute period of fire resistance.


On the basis of a risk profile of ‘A1’, Table 18 does not recommend a limit beplaced on the maximum compartment area of a storey.



15. Worked example – mixed-risk profilebuilding

The example building has six storeys (ground floor plus five others) andcomprises the following types of purpose:

• retail (clothing) on the ground floor;• restaurants and conference on the first floor;• offices on the second floor;• guest rooms on the third, fourth and fifth floors.

Escape from the ground floor is independent of escape from all other levels.Escape stairs within the building serve all storeys above the ground floor and havelobby protection. The building will adopt a simultaneous evacuation strategy.

The floor to ceiling height on all levels is between 2.5 m and 3 m and all storeyshave a gross floor area of less than 2,000 m2.


The risk profiles within the building are determined by a combination of thelikely fire growth and the occupant characteristics within each space. From therisk profile, the minimum fire protection measures, means of escape layout(including stair widths, door widths, travel distance, etc.) and constructionrecommendations can be determined.


Occupants on the ground floor (retail) and first floor (restaurant and conference)will be awake, but may be unfamiliar with the space. Therefore the occupantrisk category can be defined as ‘B’ – ‘Occupants who are awake and unfamiliarwith the building’.

Occupants on the second floor (office) will be awake and familiar with thespace. Therefore the occupant risk category can be defined as ‘A’ – ‘Occupantswho are awake and familiar with the building’.


Occupants on the third, fourth and fifth floors (guest rooms) are likely to beasleep and a short-term occupancy. Therefore the occupant risk category can bedefined as ‘Ciii’ – ‘Occupants who are likely to be asleep, and short-termoccupancy’.

Fire growth

The fire load within the ground floor retail will be consistent with that expectedwithin a clothing retail unit, i.e. racks throughout the sales floor comprisingclothing, and can be approximated to a category ‘3’ – ‘fast’ fire growth.

The fire load within the first floor restaurant and conference can be approximatedto a category ‘2’ – ‘medium’ fire growth.

The fire load within the second floor offices can be approximated to a category‘2’ – ‘medium’ fire growth.

The fire load within the third, fourth and fifth floor guest rooms can be approximatedto a category ‘2’ – ‘medium’ fire growth.

The risk profiles for each storey in the building can be broken down as follows:

• B3 on the ground floor;• B2 on the first floor;• A2 on the second floor;• Ciii2 at third, fourth and fifth floors.


Having determined the risk profiles for each space within the building, it iseasy to identify the minimum recommended management level for each riskprofile.

Where the different risk profiles within the building have different recommendedmanagement levels, the most onerous should be adopted. Therefore a level 1(the highest) management level is expected throughout the building because ofthe C2 risk profile.


Worked example – mixed-risk profile building

Step 3: Identify the automatic fire detection and alarm(minimum fire protection measures in BS 9999)recommended for the building (refer to Table 6)

The means of escape provisions recommended for a space with a particular riskprofile are based upon that space having a minimum package of fire protectionmeasures. Where the individual risk profiles have different recommendedminimum packages the most onerous should be adopted throughout the building.

On the basis of the most onerous (C2 for fire detection and alarm and B2 foremergency light) the minimum package of fire protection is as follows:

• L1 automatic fire detection and alarm system; and• emergency lighting on all escape routes excluding those within guest rooms

(including external routes).

Some storeys will therefore have a higher standard of automatic fire detection andalarm than recommended, which will support variations as described in Step 4.


After the identification of the minimum fire protection measures, it is possible toidentify whether any per cent variations are allowable within the building. It ispossible to introduce variations to components associated with means of escape,i.e. travel distances and width of exits and stairs, where;


minimum within the standard for the selected risk profile and will be providedwithin the building.

As stated at the beginning of the example the building incorporates floor toceiling heights between 2.5 to 3 m and therefore a per cent variation is notallowable in this case.

As identified within Step 3 above, the building as a whole does necessitateautomatic fire detection and alarm to an L1 standard as a minimum to complywith the standard because of the recommendation associated with the guestrooms (C2). However, as ground (B3), first (B2) and second floors (A2) do notrequire smoke detection as a minimum on the storeys, a 15 per cent variation



associated with this fire protection feature is allowable for means of escapecomponents on those storeys only (BS 9999: Clause 19.2). Consequently, thetravel distances can be extended and widths of exits and stairs can be reducedby up to the sum of the per cent variations identified above, 15 per cent(subject to overriding maxima and minima identified within BS 9999).

Step 5: Determine the dimensions applicable to means ofescape components (refer to Tables 9, 10, 11 and Table 12)

Travel distances

On the basis of the risk profiles identified in Step 1, Table 27 highlights thecalculated travel distance after the 15 per cent variation (identified in Step 4)has been applied to the relevant risk profiles.

However, these distances must be checked against Table 9, which outlines anoverall limit on travel distances. From referring to Table 9, it can be seen thatthe upper limit is not exceeded for any of the relevant risk profiles.


On the basis of the risk profiles identified in Step 1, Table 28 highlights thecalculated width per person after the 15 per cent variation (identified in Step 4)has been applied to the relevant risk profiles.



Risk profile Maximum travel distancewhen minimum fireprotection measures areprovided


Two-waytravel

One-waytravel

Two-waytravel

One-waytravel

A2 55 m 22 m 63 m 25 m

B2 50 m 20 m 57.5 m 23 m

B3 40 m 16 m 46 m 18 m

C2 18 m 9 m 18 m 9 m


However, these widths must be checked against Table 10, which outlines anoverall limit on exit width per person. By referring to Table 10, it can be seenthat the lower limit of 5.3 mm per person for risk profile B3 is exceeded andtherefore the calculated exit width of 5.1 mm per person is not acceptable andmust be increased to the limit of 5.3 mm per person. All other risk profiles arewithin the overall limits within Table 10.

Vertical exit widths – even distribution of occupants entering a stair

Where the occupant load entering an escape stair at each level served is evenlydistributed throughout the height of the stair then the width of the stair shouldbe based upon the following:

• total number of floors served by the stair; and• the most onerous width per person of the risk profiles served.

The example building has escape stairs serving five of the six storeys and the riskprofiles served by the escape stairs are B2 (first floor), A2 (second floor) and C2(third, fourth and fifth floors). On the basis of stairs serving five storeys, thecalculated stair width per person for each of the risk profiles served by the stairsis shown in Table 29 (including the 15 per cent variation where identified asapplicable in Step 4).

Variations in stair widths are limited to a maximum of 25 per cent (BS 9999:Clause 19.4.4). As the variation identified in Step 4 is only 15 per cent theallowable stair widths per person stated in Table 29 are appropriate.








C2 4.4 mm per person 4.4 mm per person


The most onerous stair width per person for the example building is 2.6 mm perperson (risk profile C2); therefore this should be adopted for calculation of thestair width for the entire stair occupant load.

On the basis of the total occupant load of 1,000 persons and the width perperson of 2.6 mm per person, the minimum stair width requirement would be2,600 mm.







C2 2.6 mm per person 2.6 mm per person


200 persons

200 persons

200 persons

200 persons

200 persons

Total = 1,000 persons

(C2)

(C2)

(C2)

(A2)

(B2)

5th

4th

3rd

2nd

1st

G

Figure 26 – Assumed population of stairs in the example building,even distribution

Vertical exit widths – uneven distribution of occupants enteringa stair

In the event that the occupant load entering an escape stair at each levelserved is not evenly distributed throughout the height of the stair, i.e. one ortwo storeys are discharging a much greater occupant load into the stair thanthe other storeys, then additional checks are necessary to ensure an adequatewidth for occupants on all storeys. The following outlines the process required.

• Calculate the width of stair required using the approach outlined above foran even distribution (2.6 mm per person for the example building, seeabove).

• Undertake a width per person check on each storey, based upon therelevant risk profile for the individual storey assuming only that storey isserved by the stair. Where a single risk profile applies to a number ofcontiguous storeys, then the width per person can be based upon thatnumber of storeys.

• The largest width resultant from the local check should then be checkedagainst the width calculated using the approach for an even distribution andthe greater of the two adopted for the escape stair width.



100 persons

100 persons

100 persons

200 persons

700 persons

Total = 1,200 persons

(C2)

(C2)

(C2)

(A2)

(B2)

5th

4th

3rd

2nd

1st

G

Figure 27 – Assumed population of stairs in the example building,uneven distribution

As highlighted in Table 29, the most onerous stair width per person for theexample building was 2.6 mm per person (risk profile C2). On the basis of thetotal occupant load of 1,200 persons, the ‘uniform’ minimum stair requirementwould be 3,120 mm.

The local check needs to determine whether the calculated width of 3,120 mmwill provide sufficient exit widths for all levels. The example building has escapestairs serving the risk profiles B2 (first floor), A2 (second floor) and C2 (third,fourth and fifth floors). On the basis of stairs serving one storey for A2 and B2and serving three contiguous storeys for C2, the calculated stair width perperson for each of the risk profiles served by the stairs is shown in Table 30(including the 15 per cent variation where identified as applicable in Step 4).

As the variation identified in Step 4 is only 15 per cent, the allowable stairwidths per person stated in Table 30 are appropriate.

Table 30 highlights that a stair width of at least 2,856 mm is required to ensurethat each individual level has an adequate exit width. As the value of 3,120 mmcalculated for the total occupant load of the stair is larger than this value theminimum stair width required for the example building is 3,120 mm.



Risk profile

(No. of floorsbeingassessed)

Minimumwidth perperson withminimum fireprotectionmeasures

Calculatedwidth perperson (withidentified 15per centvariationwhereapplicable)

Number ofpersons

Minimumwidthrequired forrisk profile

A2 (1 floor) 4.5 mm perperson

3.82 mm perperson

200 ,764 mm

B2 (1 floor) 4.8 mm perperson

4.08 mm perperson

700 2,856 mm

C2 (3 floors) 3.4 mm perperson

3.4 mm perperson

300 1,020 mm



Table 15 highlights the minimum fire resistance period recommended for thevarious construction components throughout a building. Where the number (ofminutes) is not provided or applicable, it makes reference to Table 16. Table 16can be used only where the ventilation conditions of Table 17 have been met,otherwise reference should be made to the British Standard. For the purpose ofthis example it is assumed that the ventilation conditions of Table 17 can be metfor all risk profiles.

Where the different risk profiles have different recommended periods of fireresistance the most onerous should be adopted throughout the building.

On the basis of risk profiles A2, B2, B3 and Ciii2 within a building having a topfloor not more than 18 m above ground, Table 16 would recommend aminimum 75 minute period of fire resistance as this is the most onerous (B3) forthe risk profiles within the building.

As risk profile B3 is located at the first floor and is the risk profile requiring the75 minute period of fire resistance, it would be possible to provide a compartmentfloor on the second floor with a 75 minute period of fire resistance and then toapply a 60 minute period (A2, B2 and Ciii2) of fire resistance to all storeys above.


On the basis of risk profiles A2, B2, B3 and Ciii2 within a building having a topfloor not more than 18 m above ground, Table 18 recommends a 2,000 m2 limitbe placed on the maximum compartment area of a storey because of thepresence of risk profile B3.

As the gross floor area of each storey is less than 2,000 m2 there is nocompartment floor area limitation that would need to be incorporated withinthe example building.

Every floor within a building containing a Ciii risk profile should be designatedas a compartment floor (of BS 9999: Clause 32.4.4). This recommendation isspecific to risk profiles Cii and Ciii only.



Bibliography

Standards

BS 476 (all parts), Fire tests on building materials and structures

BS 1634-1, Fire resistance and smoke control tests for door, shutter and openablewindow assemblies and elements of building hardware — Fire resistance testsfor doors, shutters and openable windows, 2008

BS 5306-2, Fire extinguishing installations and equipment on premises —Specification for sprinkler systems, 1990

BS 5588 (all parts), Fire precautions in the design, construction and use ofbuildings

BS 5651, Method for cleansing and wetting procedures for use in the assessmentof the effect of cleansing and wetting on the flammability of textile fabrics andfabric assemblies, 1989

BS 5839-1, Fire detection and fire alarm systems for buildings — Code ofpractice for system design, installation, commissioning and maintenance, 2002

BS 5852, Methods of test for assessment of the ignitability of upholsteredseating by smouldering and flaming ignition sources, 2006

BS 5867-2, Fabrics for curtains, drapes and window blinds. Flammabilityrequirements, 2008

BS 7273-4, Code of practice for the operation of fire protection measures —Actuation of release mechanisms for doors, 2007

BS 7346-4, Components for smoke and heat control systems — Functionalrecommendations and calculation methods for smoke and heat exhaustventilation systems, employing steady-state design fires — Code of practice,2003

BS 7346-7, Components for smoke and heat control systems — Code of practiceon functional recommendations and calculation methods for smoke and heatcontrol systems for covered car parks, 2006


BS 8300, Design of buildings and their approaches to meet the needs ofdisabled people — Code of practice, 2009

BS 9999, Code of practice for fire safety in the design, management and useof buildings, 2008

BS EN 81-1, Safety rules for the construction and installation of lifts — Electriclifts, 1998

BS EN 81-2, Safety rules for the construction and installation of lifts — Hydrauliclifts, 1998

BS EN 81-72, Safety rules for the construction and installation of lifts —Particular applications for passenger and goods passenger lifts — Firefighterslifts, 2003

BS EN 12845, Fixed firefighting systems — Automatic sprinkler systems —Design, installation and maintenance, 2004

BS EN 13501 (all parts), Fire classification of construction products and buildingElements

PD 7974-2, Application of fire safety engineering principles to the design ofbuildings. Spread of smoke and toxic gases within and beyond the enclosure oforigin (Sub-system 2), 2002

Books/booklets

Appraisal of Existing Structures, 3rd edition, IStructE

Fire Engineering, CIBSE Guide E, 2003

FPA Guide: Essential Principles and Guidance, published by the Arson ControlForum, Arson Prevention Bureau and Zurich Municipal

Guide to the Advanced Fire Safety Engineering of Structures, IStructE, 2007

Introduction to the Fire Safety Engineering of Structures, IStructE, 2003

Increasing the fire resistance of existing timber floors, Building ResearchEstablishment, 1988


Bibliography

Kirby et al., A New Approach to Specifying Fire Resistance Periods, StructuralEngineer, October 2004

LPC Design Guide for the Fire Protection of Buildings, 2000

The Technical Standards for Places of Entertainment, produced by The Associationof British Theatre Technicians, the District Surveyors Association, the Institute ofLicensing, 2008

Legislation

BR 187, External fire spread: building separation and boundary distances,Building Research Establishment, 1991

BR 368, Design methodologies for smoke and heat exhaust ventilation, BuildingResearch Establishment, 1999

GREAT BRITAIN. Building Regulations 2000 and subsequent amendments, TheStationery Office

GREAT BRITAIN. Regulatory Reform (Fire Safety) Order 2005, The StationeryOffice

The Building Regulations 2000 — Approved Document B — Volume 2: Firesafety — Buildings other than dwellinghouses, The Stationery Office, 2000


Bibliography

Figures

Figure 1 – Circle of fire safety 8

Figure 2 – Process for approach to risk profile and related fireprotection measures 18

Figure 3 – Design options 22

Figure 4 – Process to design and construct a building that can bemanaged 35

Figure 5 – Design for means of escape – decision chart 41

Figure 6 – Pre-movement time as a function of fire growth rate 42

Figure 7 – Fire growth, means of escape and travel time (adaptedfrom Figure 1, BS 9999) 43

Figure 8 – Travel distance 45° or more apart (BS 9999: Figure 5) 52

Figure 9 – Inner room and access room (BS 9999: Figure 6) 53

Figure 10 – Dead-end corridors (BS 9999: Figure 9) 54

Figure 11 – Progressive horizontal evacuation (BS 9999: Figure 12) 55

Figure 12 – External protection to protected stairways(BS 9999: Figure 14) 56

Figure 13 Fire resistance of areas adjacent to external stairs(BS 9999: Figure 15) 56

Figure 14 – Summary of recommendations for internal fire-fightingprovisions 63

Figure 15 – Principles for the layout and fire resistance of fire-fighting shafts (BS 9999: Figure 16) 65

Figure 16 – Route for determining the applicable fire resistanceperiods 72

The BS 9999 Handbook xiii

Contents

Figure 17 – Compartment floors (BS 9999: Figure 24) 83

Figure 18 – Small unprotected areas allowable without calculation(BS 9999: Figure 41) 88

Figure 19 – Provisions for external surfaces of walls(BS 9999: Figure 45) 89

Figure 20 – Example of smoke plume movement 92

Figure 21 – Occupancy characteristic A (awake andfamiliar) – 18 m or less in height, open or closed, simultaneousevacuation (BS 9999: Figure C.8 – Exemplar 2) 93

Figure 22 – Occupancy characteristic B (awake andunfamiliar) – 18 m or less in height, open, simultaneous evacuation(BS 9999: Figure C.24 – Exemplar 12) 94

Figure 23 – Occupancy characteristic B (awake and unfamiliar) –18 m or less in height, enclosed, fire-resisting, simultaneousevacuation (BS 9999: Figure C.25 – Exemplar 13) 95

Figure 24 – Occupancy characteristic Ciii (asleep and unfamiliar) –Short-term occupancy, protected escape route, any height(BS 9999: Figure C.35 – Exemplar 20) 96

Figure 25 – Number of seats in a row (BS 9999: Figure D.1 andTable D.1) 100

Figure 26 – Assumed population of stairs in the example building,even distribution 124

Figure 27 – Assumed population of stairs in the example building,uneven distribution 125

xiv The BS 9999 Handbook

Contents

Tables

Table 1 – Occupancy characteristics 11

Table 2 – Fire growth rate 12

Table 3 – Risk profile (BS 9999: Table 4) 13

Table 4 – Examples of risk profiles (BS 9999: Table 5) 14

Table 5 – Checklist for the design assessment, refer to Figure 2(BS 9999: Table 1) 19

Table 6 – Summary of the minimum fire protection package for eachrisk profile (BS 9999: Tables 6, 8 and 9) 25

Table 7 – Key factors used in assessing management levels 31

Table 8 – Permissible variation of door, corridor and stair widths andtravel distance with ceiling height (BS 9999: Table 16) 45

Table 9 – Travel distance as a function of risk profile(BS 9999: Tables 12 and 17) 46

Table 10 – Door width as a function of risk profile – mm per person(BS 9999: Tables 13 and 18) 47

Table 11 – Absolute minimum width of stairs (BS 9999: Table 14) 48

Table 12 – Minimum width of escape stairs for simultaneous evacuation(BS 9999: Table 15) 49

Table 13 – Examples of typical floor space factors (BS 9999: Table 10) 50

Table 14 – Perimeter access requirements for fire service vehicles(BS 9999: Table 21) 62

Table 15 – Minimum fire resistance performance (BS 9999: Table 24) 73

Table 16 – Fire resistance periods for elements of structure (based onthe ventilation conditions) (BS 9999: Table 26) 78

The BS 9999 Handbook xi

Contents

Table 17 – Ventilation conditions for application of Table 16(BS 9999: Table 27) 80

Table 18 – Maximum dimensions of compartments (BS 9999: Table 30) 81

Table 19 – Provision of fire doors (BS 9999: Table 32) 85

Table 20 – Maximum travel distances for weather-housed, weather-protected or external plant (BS 9999: Table F.1) 107

Table 21 – Calculated travel distances 112

Table 22 – Calculated horizontal exit width per person 112

Table 23 – Calculated vertical exit width per person 112








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