Jayeadra - NFPA€¦ · NFPA 92B-- A95 ROP on theoretical generalizations of the limited amount of...

Report of the Committee on

Smoke Management Systems

Harold E. Nelson, Chair Hughes Assoc., Inc., MD

Elyahu (Ell) Avidor, Professional Loss Control Ltd., Canada Donald W. Belles, Donald W. Belles & Assoc., Inc., TN

Rep. American Architetural Mfrs. Assoc. $1~k B. Buckley, Houston, TX

omas C. Campbell, Saratoga, CA Rep. North American Insulation Mfrs. Assoc.

Elmer F. Chapman, NewYork Fire Dept., NY Gregory F. DeLuga, Landis & Gyr Powers, Inc., IL Michael Earl Dillon, Dillon Consulting Engr, Inc., CA S. E. Egesdal, Honeywell, Inc., IL

Rep. Nat'l Electrical Mfrs. Assoc. Charles Green, Colt Int'l Ltd, England Gunnar Heskestad, Factory Mutual Research Corp., MA William R. Houser, U.S. Army Environmental Hygiene Agency, MD DanieIJ. Kaiser, Underwriters Laboratories Inc., IL Ohn E. Kampmeyer, Malda Engineering, Inc., PA

hn H. Klote, NIST/Building and FireResearch Laboratory, MD rancisJ. McCabe, Prefco Products, PA

James A. Milke, University of Maryland, MD Gregory R. Miller, Code Consultants, Inc., MO Lyman (Lew) Parks, Bellcore, NJ Zenon A. Pihut, Texas Dept. of Health, TX J~lhn (Sonny) Scarff, Marriott Corp., DC

iliam A. Schmidt, Bowie, MD Todd E. Schumann, Industrial Risk Insurers, IL JG" Brooks Semple, Smoke/Fire Risk Mgmt., Inc., VA

eorge T. Tamura, Nat'l Research Council Canada, Canada Robert Van Becelaere, Ruskin Mfg., Div, MO

Rep. Air Movement & Control Assn., Inc. Thomas E. Waterman, Inst. for Advanced Safety Studies, IL William A. Webb, RolfJensen & Assoc., Inc., IL

Alternates

Eric Anderson, System Sensor - Attway, IL (Air. to S. E. Egesdal)

Daniel L. Arnold, RolfJensen & Assoc., Inc~, GA (Alt. to W. A. Webb)

Richard J. Davis, Factory Mutual Research Corp., MA (Alt. to G. Heskestad)

Victor L. Dubrowski, de Consultants Inc., MO (Alt. to G. R. Miller)

Gary D. Loagheed, Nat'l Research Council, Canada (Alt. to G. T. Tamura)

Geraldine Massey, Dillon Consulting Engr, Inc., CA (Alt. to M. E. Dillon)

Jayeadra S. Parikh, Underwriters Laboratories Inc., IL (Alt. to D.J. Kaiser)

Richard M.Pletmer, Greenheck Fan Corp., WI (Alt. to IL Van Becelaere)

PeterJ. Gore Willse, Industrial Risk Insurers, CT (Alt. to T. E. Schumann)

Nonvoting

Bent A. Borresen, Techno Consultant, Norway (AlL to C. N. Madsen)

E. G. Butcher, Fire Check Consultants, England (Alt. to A. G. Parnell)

Christian Norgaard Madsen, Techno Consultant, Norway Alan G. Parnell, Fire Check Consultants, England

Staff Liaison: Ron Cot6

This list represents the membership at the time the Committee was balloted on the text of this edition. Since that time, changes in the membership may have occurred.

Committee Scope: This Committee shall have primary responsibil- ity for documents on the design, installation, testing, operation and maintenance of systems for the control, removal or venting of heat or smoke from fires in buildings.

The Report of the Committee on Smoke Management Systems is presented for adoption.

This Report was prepared by the Technical Committee on Smoke Management Systems and proposes for adoption amendments to NFPA 92B-1991, Guide for Smoke Management Systems in Malls, Atria, and Large Areas. NFPA 9213-1991 is published in Volume 10 of the 1994 National Fire Codes and in separate pamphlet form.

This Report has been submitted to letter ballot of the Technical Committee on Smoke Management Systems which consists of 28 voting members; of whom 26 voted affirmatively, 1 negatively (Mr. Campbell), and l ballot was not returned (Mr. Scarff).

Mr. Campbell substantiated his negative vote with the following: "I find the definition of "A" in Section 3-5.2.1 to be confusing. I wonder if we are talking about the floor area, the horizontal area

of a section at some height in a tapered atrium, or the vertical cross- sectional area? ff we mean a vertical section, are we measuring it across the width or along the length of the space? After reading the Appendix item for this section, I think we mean the area of a vertical section across the small dimension of a rectangular space.

One should not have to go the Appendix to figure this out. I suggest that the definition be changed to read:

A = vertical cross-sectional area of the space being filled with smoke, measured across the width of the space (ft2)."

Mr. Dillon and Dr. Heskestad, although voting affirmatively, provided the following comments:

Mr. Dillon: "I am casting an affirmative vote reluctantly for the sole

~ urpose of putting the material out for public comment. I TRONGLY believe that much of this material lacks sufficient caveat

notice to the user and if misused could wreak great havoc."

Dr. Heskestad: "Note, however, that new Section 3-5 (Log #CPI 1) still has many unexplained symbols (X sub L, Qsub c, rho sub o, tau, and gamma) and mathematically undefined symbols (D, D sub m). Can this be remedied editorially?"

23

N F P A 9 2 B - - A95 R O P

(Log #CP1) 92B- 1 - (1-2): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise as follows:

1-2" Scope. This guide provides methodologies to estimate the location of smoke within a large volume space from a fire either in the large volume space or an adjacent space. These methodologies comprise the technical basis to assist in the design, installation, testing, operation and maintenance of new and retrofitted smoke management systems in buildings having large volume spaces for the management of smoke within the space where the fire exists or between spaces not separated by smoke barriers. Such buildings include those with atria, covered malls, and similar large volume spaces. See NFPA 92A, Recommended Practice for Smoke Control Systems, for mechanical smoke control between fire-compartmented building spaces separated by smoke barriers and NFPA 204M, Guide for Smoke and Heat Venting, for gravityventing. This guide is not intended to apply to warehouses, manufacturing facilities, or other similar spaces. This guide does not provide methodologies to assess the effects of smoke exposure on people, property or mission continuity. SUBSTANTIATION: To clarify the scope. COMMITTEE ACTION: Accept.

(Log #CP2) 9213- 2 - (1-4 Ceiling Jet): Accept SUBMI'ITI~Pa Technical Committee on Smoke Management Systems, RECOMMENDATION: Add definition as follows:

Ceiling Jet. A flow of smoke under the ceiling, extending radially from the point of fire plume impin~.ement on the ceiling. Normally, the temperature of the ceiling je t will be greater than the adjacent smoke layer. SUBSTANTIATION: Per TIA 91-2. Change included to account for fire where heat release rate increases, decreases, then increases a "n. ~ O I ~ I ' I ~ E E ACTION: Accept.

(Log #6) 92B- 3 - (1-4 Fire Fighters' Smoke-Control Station (FSCS) (New)):

MITTER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: Add new definition:

Fire Fighters' Smoke-Control Station (FSCS). The fire fighters' smoke-control station should provide full monitoring and manual control capability over all smoke-control systems and equipment. SUBSTANTIATION: Fire Fighters' Smoke-Control Station is a very useful concept contained in NFPA 92A, 1993 edition. This proposal brings NFPA 92B into harmony with NFPA 92A. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: Proposed definition is not the same as the definition in NFPA 92A and the substantiation is more of a statement of fact rather than ajnstification.

(Log #CP32) 92B-4- (1-4 Smoke Damper): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise as follows:

Change the last sentence of the definition of "Smoke Damper" to read: A combination fire and smoke damper fl~tfl~t meet~ the requirements of UL 555, Standard for Fire Dampers, and UL 555S, Standard for Leakage Rated Dampers for Use in Smoke Control Systems. SUBSTANTIATION: For clarity. COMMITrEE ACTION: Accept.

(Log #CP3) 92B- 5 - (1-4 Smoke Layer Interface): Accept SUBMITTER= Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise definition as follows: Smoke Layer Interface. The theoretical boundary between a smoke

layer and smoke-free air, as depicted in Figure 1-4. In practice, the smoke layer interface is an effective boundary within a transition buffer zone which can be several feet thick. Below this effective

boundary, the smoke density in the transition zone decreases to zero.

~Ceiling

Smoke l a y e r £ n t a z f a c e Equat£ons 1 4 , 1 5 , 1 7 & 21

Fizst £ n d ~ c a t i o n o f smok~ Equations 9 & i0

¥1oor

Figure 1-4 Smoke layer interface.

SUBSTANTIATION: Per TIA 91-3. The modification to the definition is needed as part of the Section 3-5.2 changes .(TIA 92B- 91-3) relating to the application of equations (9) and (10). The change will assist in distinguishing between the smoke layer interface and the first indication of smoke. COMMr[TEE ACTION: Accept.

(Log #5) 92B- 6 - (1-4 Smoke Removal): Reject SUBMITrER: MichaelJ. Aniello, Port Jefferson station, NY RECOMMENDATION: None. SUBSTANTIATION: I would like to submit this smoke removal

~ an to the proper authority, so that they can solve why the Fire epartment in New York City stopped the installation of this plan

because the spraying of water on the fusible link was against the Fire Code. COMMITTEE ACTION: Reject. COMMITrEE STATEMENT: Submitter did not provide a recommendation.

(Log #'2) 92B- 7- (1-4, 3-3.4, 3-3.5): Accept in Principle SUBMITTER: James Milke, University of Maryland at College Park RECOMMENDATION: The proposed TIAwas developed utilizing legislative text. Lined-out text indicates deletions. Underlined text indicates added text.

1. Add a new definition to Section 1-4 to read: CeilingJet. A flow of smoke under the ceiling, extending radially

from the point of fire plume impingement on the ceiling. The temperature of the ceiling jet will be greater than the adjacent smoke layer.

2. Revise 3-3.4 to read: Steady Fires. For radius-to-ceiling height ratios less than approxi-

mately 0.6, file temperature rise of the smoke ~ad¢; :I.~ ~ ; ik . s within the ceilingie¢ can be estimated as a function of time based

24

NFPA 92B-- A95 ROP

on theoretical generalizations of the limited amount of experimental data [40 ]. For X_< 480 100 :

X-- 4.6 x 10-4y2 + 2 .7x 10-15 Y6

where

(s)

X = t Q 1 / 3 / H 4 / 3

y = A T H 5 / 3 / Q 2 / 3

and where

t = time from ignition(s) Q = heat release rate (steady fire) (Btu/s) H = ceiling height above fire surface (ft) AT = temperature rise within ceiling iet (°F)

Equation (3) is based on experimental data from investigations in rooms of varying shapes, characterized by the ratio of the cross- sectional area o f the room to the square of the height of the room ( A / H 2 ) . The rooms include those with A /H2 of 0.9 (in a quiescent room) to 7.0 (in a room with mechanical ventilation at a rate of 1.0 air changes per hour) and smooth ceilings without obstructions [10, 15]. Use of equation (3) for A / H 2 > 7.0 tends to overestimate the temperature rise at advanced times.

3. Add a reference to 3-3.4 to read: 26. Heskestad. G. and Delichatsios. M.A.. "Uodate: The Initial

Convective Flow in Fire." Fire Safety Iournal. 1"5. o. 471 (1989A - v

4. Revise 3-3.5 to read: Unsteady Fires. For t-square fires (see Equation (2)], the tempera-

ture rise of the smoke ~a~c, tLc cc~l;,Jg within the ceilin~j¢~ associated with radius-to-ceiling height ratios less than approximately 0.6 can be estimated as a function of time based on theoretical generalizations of the limited amount of experimental data {-14~.

AT = 27,400 [ t / ( tg 2/5 H4/5 )-0.22]4/3/[tg 4/5 H3/5 ] (4)

(AT in °F; and tg in s; H in ft).

Enuation (4~ is based on a widely accented emnirical correlation from investkrations with extensive, smooth, unobstructed ceilings [9.261. evaluated at r/H=0.3. Eouation (4) was then verified awainst Other exnerimental data with a limited cei]in~ [ 10l. where A/ lq2

4~0s and a ventilation rate of 1.0 air c[mn~e her hour. on (4) is most accurate i f A / H ~ >7.4.t~ _q~80s. and the

ventilation rate does no t exceed 1.0 air chan~'e her ho~lr, SUBSTANTIATION: The proposed changes address two important areas of concern. First, in 3-3.4, the limit of X of 480 is incorrect, being the value only for metric units. Second, numerous questions have been raised concerning the applicability of the equations in these sections. In many cases, the questions indicate a lack of understanding of the basis or applicability of the equations in these sections. Thus, these changes are needed to clarify the applicability of the equations so that users may properly interpret the results. The clarification included is based on a letter to the editor of Fire Technology by Heskestad (May, 1991),

The new definition for ceiling j e t is needed to support the changes in $-3.4 and 3-3.5.

The equations in these two sections are important for the estima- tion of t he time to response of ceiling-mounted spot detectors, which may be used to activate the smoke management system. Without the proper changes, users will not be able to appreciate the assumptions used to formulate these expressions. Consequently, the equations may be misapplied, leading to inappropriate. . . design assumptions. Because of the danger of misapplication of the equations, I suggest that this proposed set o f changes is of an immediate nature, thereby justifying p rompt corrective action via a TIA. At a recent meet ing of the Technical Committee on Smoke Management Systems, this proposed set of changes was unanimously supported by those in attendance. COMMITrEE ACTION: Accept in Principle. See Committee Action on Proposals 92B-2 (Log #CP2) and 92B-20

(Log #CP10). COMMrI'rEI~ STATEMENT: The actions taken on Committee Proposals 9217,-2 (Log #CP2) and 92B-20 (Log #CP10) should satisfy the submitter 's intent.

(Log #1 ) 92B- 8 - (1-4, 5-5.2.1, 3-5.2.2): Accept in Principle SuBMrrTER= James Milke, University of Maryland at College Park RECOMMENDATION: 1. Revise Section 1-4 definition of Smoke Layer Interface to read:

1-4 Smoke Layer Interface. The theoretical boundary between a smoke layer and smoke-free air, as depicted in Figure 1-4. In practice, the smoke layer interface is an effective boundary within a transition buffer zone which can be several feet thick. Below this effective boundary, the smoke density in the transition zone decreases to zero.

For a copy of figure submitted, see Proposal 92B-5 (Log #CP3)

2. Revise 3-5.2.1 to read: 3-5.2.1 Steady Fires. For steady fires, the height o f the initial

indications of smoke above the fire surface, z, can be estimated for any time, t, f rom the Equation (9) (where calculations yielding z / H > 1.0 mean that the smoke layer has not yet begun to descent)-

z / H = 0.67- 0.28 In[ tQ1/3 / H4 /3 ) / ( A / H 2 ) ] (9)

where z = height of the first indications of smoke above the fire surface

fit) H = ceiling height above the fire surface (ft) t = time(s) Q = heat release rate from steady fires (Btu/s) A = cross-sectional area of the space being filled with smoke (ft2)

Equation (9) is based on experimental data from investigations with A / H 2 ratios in the range from 0.9 to 14 and for values of z / H >_ 0.2 [7, 10, 12, 13, 14]. This equation is for the worst case condition, a fire away from any walls. The equation provides a conservative estimate of hazard because z relates to the height where there is a first indication of smoke rather than the smoke layer interface position.

3. Revise 3-5.2.2 to read: 3-5.2.2 Unsteady Fires. The descent of the height of the initial

indications of smoke can also be estimated for certain types of unsteady fires, e.g., t-square fires. From basic theory and limited experimental evidence, the height of the initial indications of the smoke above the fire surface, z, can be estimated for a given time according to the following relation (where calculations yielding z / H > 1.0 mean that the smoke layer has not yet begun to descent):

z / n = 0 .23 [ t / ( t g2 /5 H4/5 ( A / H 2 ) 3 / 5 )] -1.45 (10)

(t and tg in s; H in ft; A in ft2 ; as previously defined)

Equation (10) is based on experimental data from investigations with A / H 2 ratios in the range from 1.0 to 23 and for values of z / H > 0.2 [10]. This equation is for the worst case condition, a fire away from any walls. The equation also provides a conservative estimate of hazard because z relates to the height where there is a first indication of smoke rather than the smoke layer interface position. SUBSTANTIATION: The proposal includes clarifications based on a letter to the editor of Fire Technology by Heskestad (May, 1991). The essence of these changes is to clarify the applicability of equadous (9) and (10), especially relative to the definition ofz. In

~ articular, users may treat the smoke layer interface position and the eight, z, as being interchangeable. Given that z relates to the first

indication of smoke, the smoke immediately above that position is not generally expected to pose a significant th rea t Consequently, application of the equations to formulate a design based on these equations may be overly conservative i fz is misinterpreted to refer to the smoke layer interface position.

In addition, the changes identify the limitations of the equations, specifically that the equations should not be used for z/H-< 0.2, e.g., for conditions where the first indication of smoke is approaching the floor of the space. Many of the questions which have been raised concerning the validity of these equations have focused on counter- intuitive results for situations where z / H < 0.2. Given that no data is available for z / H < 0.2, these concerns can nei ther be verified or refuted. The proposed modification to the definition of smoke layer

interface is needed as part of the suggested changes for 3-5.2, relating to the application of equations (9) and (10). The change to the definition will assist in distinguishing between the smoke layer interface and the first indication of smoke.

Because of the danger of misapplication of the equations, I suggest that this proposed set of changes is of an immediate nature, thereby justifying prompt corrective action via a TIA. At a recent meet ing of

NFPA 92B-- A95 ROP

the Technical Committee on Smoke Management Systems, held on November 9, 1992, in Arlington, VA, this proposed set of changes was unanimously supported by those in attendance. COMMITTEE ACTION: Accept in Principle. See Committee Action on 92B-5 (Log #CP3) and 92B-22 (Log

#CP12). COMMITrEE STATEMENT: The action taken on Committee Proposals 92B-5 (Log #CP3) and 92B.-22 (Log #CP12) should satsify the submitter's in ten t

(Log #CP4) 92B- 9 - (1-5.1.1): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add the following wording to the end of the first paragraph:

As a result of the zone model approach, the model assumes uniform properties (smoke concentration and temperature) from the point of interface through the ceiling and horizontally throughout the entire smoke layer. SUBSTANTIATION: The added phrase is important to identify limitations of calculations. COMMITTEE ACTION: Accept

(Log #CPS) 92B- 10 - (1-5.1.2): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Renumber the second paragraph in 1-5.1.1 as 1-5.1.2 and renumber subsequent paragraphs as necessary. SUBSTANTIATION: To separate in two sections the issues of zone

roach and entrainment. E ACTION: Accept

(Log #CP6) 92B- 11 - (1-5.5): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Change 1-5.5 to read:

1-5.50nerat in~ Conditions. The smoke management system components should be ~ rnted-f~ continuous use at the maximum temperature expected, using calculations contained in this guide. SUBSTANTIATION: For consistency and to cover the many "unrated" fans that may be capable of operating continuously given a low temperature rise scenario as may be expected in a high ceiling space. COMMITTEE ACTION: Accept

(Log #CP7) 92B- 12 - (1-5.6 (New)): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add the following:

1-5.6 Tenability Analysis. When the design is based on maintaining tenability of a portion of space, one of two approaches can be pursued. First, the design may depend on preventing the development of a smoke layer in that portion of the space. Second, the design may be based on comparing the qualiues of a smoke layer to hazard threshold values to demonstratethat the tenability of the space is maintained. Such a demonstration requires that the effects of smoke on people be evaluated. Such an evaluation is outside the scope of this guide. However, other references are available which

~ resent analytical methods for tenability analyses [ 34]. UBSTANTIATION: Comments are included throughout the

document that a possible design basis involves maintaining tenability. Yet, no guidance is provided within the guide on how to conduct such an analysis. COMMITTEE ACTION: Accept.

(Log #7) 92B- 13 - (2-3.1): Reject SUBMITTER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: These fault analysis considerations should be reflected in the design of all displays and monitoring panels of the Fire Fighters' Smoke-Control Station.

Insert a f t e r . . . "and the probability of such occurrence should be determined." SUBSTANTIATION: This proposal ensures that the benefits of the fault analysis will be actually available to the fire department in the event of a fire. COMMITrEE ACTION: Reject. COMMI'FrEE STATEMENT: See Committee Action on Proposal 92B-3 (Log #6).

(Log #8) 92B- 14- (2-3.2): Reject SUBMITTER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: These reliability considerations should be reflected in the design of all displays and monitoring panels of the Fire Fighters' Smoke-Control Station.

Insert a f ter . . . "by providing a timely visual or audible indication of components failure and will facilitate prompt repair." SUBSTANTIATION: This proposal ensures that a reliable smoke management system will be actually available to the fire department in the event of a fire. COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: See Committee Action on Proposal 92B-3 (Log #6).

(Log #9) 92B- 15 - (2-3.3): Reject SUBM]TTER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: These periodic testing considerations should be reflected in the design of all displays and monitoring panels of the Fire Fighters' Smoke-Contro/Station.

Insert a f te r . . . " i t is desirable that, where possible, instrumentation be completely built-in or partially built-in and partially provided as

~ ortable monitors." UBSTANTIATION: This proposal ensures that the benefits of

periodic testing will be actually available to the fire d e p a ~ n e n t in the event of a fire. COMMITYEE ACTION: Reject. COMMITrEE STATEMENT: See Committee Action on Proposal 92B-3 (Log #6).

(Log #3) 92B- 16 - (2-4.2.2): Accept SUBMITrER: Joseph A. Drouin, Gardner, MA RECOMMENDATION: Delete "NFPA 71, Standard for the Installation, Maintenance, and Use of Protective Signaling Systems."

Replace "NFPA 72, Standard for the Installation, Maintenance, and Use of Protective Signaling Systems" with "NFPA 72, National Fire Alarm Code." SUBSTANTIATION: NFPA 71 has been incorporated into the NFPA 72-1993, National Fire Alarm Code. COMMITTEE ACTION: Accept

(Log #10) 92B- 17 - (2-4.3): Reject SUBMITTER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: These manual activation considerations should be reflected in the design of all displays and monitoring panels of the Fire Fighters' Smoke-Control Station.

Insert a f ter . . . "A means of manually starting and stopping the smoke management system should be at a location accebsible to the fire department."

SUBSTANTIATION: This proposal ensures that the benefits of periodic testing will be actually available to the fire department in the event of a fire. COMMITYEE ACTION: Reject. COMMITrEE STATEMENT: See Committee Action on Proposal 92B-3 (Log #6).

26

NFPA 9 2 B - - A95 ROP

(Log #CP8) 92B- 18 - (3-1.1, 5-1.9 and 3-1.$): Accept SUBMIT]~R: Technical Gommittee on Smoke Management Systems, RECOMMENDATION: Replace current 3-1.1 and 5-1.9 with the following 5-1.1 through 5-1.$. Renumber current 5-1.$ and 5-1.4 as 5-1.4 and 5-1.5.

5-1.1 Available Approaches. Three different approaches are available:

a. Scale modeling using a reduced scale physical model following established scaling laws. Small scale tests are then conducted to determine the requirements and capabilities of the modeled smoke management system.

b. Algebraic, closed form equations derived primarily from the correlation of large and small scale experimental results.

c. Compar tment fire models using both theory and empirically derived values to estimate conditions in a space.

Each approach has values and limitations. None is totally satisfac- tory. While the results obtained from the different approaches should normally be similar, they are no t usually identical. The state- of-the-art involved, while advanced, is empirically based and a final theory provable in fundamental physics has not yet been developed. The core of each of the calculation methods is based on the ent ra inment of air (or other surrounding gases) into the rising fire driven plume. Avariation of approximately 20% in entra inment occurs between the empirically derived entra inment equations commonly used, such as those indicated in this chapter or in zone type compar tment fire models. Users maywish to add an appropriate safety factor to exhaust capacities to account for this uncertainty. A brief discnssion of the values of the several approaches follows.

5-1.1.1 Scale Modeling. Scale modeling is especially desirable when the space being evaluated has projections or other unusual arrangements that prevent a free rising plume. In a scale model, the model is normally proport ional in all dimensions to the actual building. The size of the fire and the interpretation of the results are, however, governed by the scaling laws (as given in 5-1.9). While sound, the approach is expensive, t ime-consuming and valid only within the range of tests conducted. Since this approach is usually reserved for complex structures it is important that the test series cover all of the potential variations in factors such as position and size of fire, location and capacity of exhaust and intake flows, variations in internal temperature (stratification or floor ceiling temperature gradients), and other variables. It is likely that de t&t ion will not be appraisable using scale models.

3-1.1.9 Algebraic Equations. Algebraic equations, as contained in this guide, provide a desk top means of calculating individual factors that collecuvely can be used to establish the design requirements of a smoke management system. The equations presented are considered to be the most accurate, simple, algebraic expressions available for the proposed purposes. In general, they are limited to cases involving fires that burn at a constant rate of heat release (Steady Fires as described in 5-9.2) or fires that increase in rate of heat release as a function of the square of time (Unsteady Fires as described in 5-9.$). The equations are not appropriate for other fire conditions or for a condition that initially grows as a function of time but after reaching a maximum burns at a steady state. In most cases j'udicions use of the equations, can reasonably overcome, this . limitation. Each of the equations has been derived from experimental data. In some cases there is only limited test data a n d / o r the data has been collected within a limited set of fire sizes, space dimensions, or points of measurement. Where possible, comments are included on the range of data used in deriving the equations presented. It is important to consider these limits.

Caution should be exercised in using the equations to solve the variables other than the ones presented to the left of the equal sign, unless it is clear how sensitive the result is to minor changes in any of the variables involved. When these restrictions present a limit that obstructs the users' needs, consideration s h o u l d b e given to combining the use of equations with either scale or compal~nent fire models. Users of the equations should appreciate the sensitivity of changes in the variables be ing solved for.

5-1.1.$* Compar tment Fire Models. Computer capabilities sufficient to execute some of the family of comparunent fire models are widely available. All compar tment fire models solve the conservation equations for distinct regions (control volumes). Gompar tmentf i re models can be generally classed as zone models or field (computational fluid dynamics) models.

a. Zone Models. Zone models are the simpler models and can generally be run on personal computers. Zone models usually divide the space into two zones, an upper zone that contains the smoke and ho t gases produced by the fire and a lower zone which is the source of en t ra inment air. The size of the two zones varies during the course of a fire, depend ing on the rate of flow from the lower to the upper zone, the rate of exhaust of the upper zone and the temperature of the smoke and gases in the upper zone. Because of the small number of zones, zone models use engineering equations for heat and mass transfer to evaluate the transfer of mass and energy from the lower to the upper zone, the heat and mass losses from the upper zone, and other special features. Generally, the equations assume that conditions are uniform in each respective zone.

In zone models, the source of the flow into the upper zone is the fire plume. All zone models have a plume equation. A few models allow the user to select among several plume equations. Most current zone models are based on an axisymmetric plume.

Because present zone models assume that there is no preexisting temperature variation in the space, they can not directly handle stratification. Zone models also assume that the ceiling smoke layer forms, instantly and evenly from wall to wall. This fails to account for the initial lateral flow of smoke across the ceiling. The resulting error can be significant in areas having large ceiling areas.

Zone models can, however, calculate many important factors in the course of events (e.g., smoke level, temperature, composition, and rate of descent) from any fire that the user can describe. Most will calculate the extent of heat loss to the space boundaries. Several will calculate the impact of vents or powered exhaust and some will predict the response of heat or smoke actuated detect ion systems.

b. Field Models. Field models (also referred to as Computational Fluid Dynamics (CFD) Models) usually require large-capacity computer work stations or mainframe computers and advanced expertise to operate and interpret. Field models, however, can potentially overcome the limitations of zone models and comple- ment or supplant scale models. As with zone models, field models solve the fundamental conserva-

tion equations. In field models, however, the space is divided into many cells (or zones) and use the conservation equations to solve the movement of heat and mass between the zones. Because of the massive number of zones, field models avoid the more generalized engineer ingequat ions used in zone models.

Through the use of small cells, field models can examine the situation in much greater detail and account for the impact or irregular shapes and unusual air movements that cannot be addressed by either zone models or algebraic equations. The level of ref inement exceeds that which can usually be observed or derived from scale models.

$-1.9 Scale Models $-1.9.1" In this guide, the emphasis of scaling activities is placed on

modeling hot gas movement through building configurations due to fire. Combustion and flame radiation p h e n o m e n a are ignored. Fire growth is not modeled. A fire must be specified in terms of a steady or time-varying heat release rate.

$-1.9.9 Based on the relationships in Table $-1.9.9, a scale model can be developed. The model should be made large enough to achieve turbulent flow of the full scale system. Scaling expressions relating full scale conditions (F) to those in a scale model (m) are presented in Table 5-1.2.2, assuming that the same ambient conditions exist.

Nomenclature for Table 3-1.2.9: c: Specific heat of enclosure materials (wall, ceiling) k: Thermal conductivity of enclosure materials (wall, ceiling) l: Length p: Pressure Q: Heat release rate t: Time T: Temperature v: Velocity V: Volumetric exhaust rate x: Position

subscripts:

F: Full-scale m: Small-scale model s: Smoke w: Wall

27

N F P A 9 2 B - - A 9 5 R O P

Table $-1.2.2 Scaling Expressions

Ambient Temperature

Smoke Temperature

Velocity

Pressure

Geometric Position

Time

Heat Release Rate

Volumetric Exhaust Rate

Wall Thermal Properties

Tm=T F

Ts,m =Ts,F

v m = v F

Pm = PF (lm/!F)

x m = x F (lm/i F)

t m = t F ~

Qm(tm) = (QF (tF) (1 m/IF) 5/2

Vfan,m (tm) = Vfan,m (IF) (ira/iF) 5/2

(kpc) w,m = (k pc) w,F (I m/I F) 0.9

3-1.3 The remainder of this section presents the algebraic equation based calculation procedures for the various design parameters, as referred to in the previous sections. The calculation procedures represent an accepted set of algebraic equations and related information available for this edition of the guide. SUBSTANTIATION: The new section 3-1.1 provides an overview of analytical and experimental methods. Also, it provides discussion to indicate emphasis of guide and presentation of algebraic equations.

Section 3-1.2 contains an expanded discussion providing the basis for formulating a scale model for evaluating the design of a smoke management system. COMMYITEE ACTION: Accept.

(Log #CPO) 92B- 19 - (3-8.2.1, 3-8.2.2.1 and 3-8.2.2.2): Accept SUBMITI'ER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise 3-3.2.1, 3-3.2.2.1 and 3-3,2.2.2 to read as follows (this proposal makes no change to paragraph 3-8.2.2):

3-3.2.1 Ceiling Mounted Spot Smoke Detectors. The response of a ceiling mounted spot smoke detector can be estimated by consider- ing a given temperature rise of the fire gases [7], depending on the Priarticular detector model and fire source. A realistic temperature

se indicative of a concentration of smoke from common fuels that would cause detection by a reasonably sensitive spot detector is approximately 20°F (approximately 10°C).

3-8.2.2.1 Steady Fires. The approximate gas temperature at actuation of automatic sprinklers can be determined from the information provided in Table 3-2, based on sprinkler response theory [8], ceiling-level gas temperatures from Equation (8), and a correlation between gas velocity and gas temperature [9]. The temperatures noted in the table are the differences between the gas temperature and the sprinkler temperature rating of approximately 165°F 474 °) at actuation for the noted ranges of RTI, celqing height, and fire size. For values not indicated in the table, linear interpolation can be used. The associated time for actuation, t, can be estimated by using Equation (3), with the temperature rise being the determined gas temperature (evaluated using Table 3-2) minus the ambient temperature.

3-3.2.2.2 Unsteady Fires. The approximate gas temperature at actuation of automatic sprinklers can be determined from the information provided in Table 3-8, based on sprinkler response theory [8], ceiling-level gas temperatures from Equation (8), and a correlation between gas velocity and gas temperature [9]. The temperatures noted in the table are the difference between the gas temperature and the sprinkler temperature rating of approximately 165°F (74°C) at actuation for the noted ranges of RTI, ceiling height, and fire growth rate, given a t-squared type fire [9]. For values.not indicated in the table, linear interpolation can be used.

I The associated time for actuation, t, can be estimated by using Equation (4), with the temperature rise being the determined gas temperature (evaluated using Table 3-3) minus the ambient temperature. SUBSTANTIATION: Added and revised discussion provides a reference used as a basis for correlation. COMMI'ITEE ACTION: Accept.

(Log #CPI 0) 928- 20 - (?,-8.4, 3-8.5): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise text as follows:

8-3.4 Steady Fires. For radius-to-ceiling height ratios less than approximately 0.6, the temperature rise of the smoke within the ceiling je t can be estimated as a function of time based on theoretical generalizations of the limited amount of experimental data. For X <100:

X = 4.6x10-4 Y2 + 2.7x10-15 y6 (3)

where X = t f ) l / 8 / H 4 / 3 y-- ,~THS/8 /Q2/3

and where t = time from ignition (s I

~ = heat release rate [steady fire] (Btu/s) ceiling height above fire surface (ft)

AT = temperature rise within ceiling je t (°F) Equation (3) is based on experimental data from investigations in

rooms ofvarylng shapes, characterized by the ratio of the cross- sectional area of the room to the square of the height of the room (A/H2 1. The rooms include those with A/H2 of 0.9 (in a quiescent room) to 7.0 (in a room with mechanical ventilation at a rate of 1.0 air change per hour) and smooth ceilings without obstructions [10,14]. Use of equation (81 for A/H2 > 7.0 tends to overestimate the temperature rise at advanced times.

Subsequent to the original formulation of equation (8), other data (A/HIZ in the range 2.3 - - 8.8) have been found which support the equation [10 (Test 19), 27-81], while some data (A/H2 ratios of 1.0 and 7.6) indicate considerably higher temperatures than predicted by the equation [82, 33]. The latter were obtained with liquid pools which may have initially burned offvapors evaporated prior to ignition.

Equation (3) incorporates effects of a gradual, although relatively quick initial rise to an approximately steady-state burning rate. Although not rigorously steady, such fire behavior appears representative of what, in practice, may be considered "steady fires".

3-8.5 Unsteady Fires. For t-square fires [see Equation (2)], the temperature rise of the smoke within the ceiling jet associated with radins-to-ceiling height ratios less than approximately 0.6 can be estimated as a function of time based on theoretical generalizations of the limited amount of experimental data:

(AT in °F a n d tg in s, H in ft).

(4)

Equation (4) is based on a widely accepted empirical correlation from investigations with extensive, smooth, unobstructed ceilings [9,26], evaluated at r / H = 0.3. Equation (4) was also verified ag2ainst other experimental data with a limited ceiling [ 10], where A/HZ = 7.4, t~ = 480 s, and a ventilation rate of 1.0 air change per hour. Equation (41 is most accurate if A/H2 ~7.4, t < 480 s and the ventilation r a t e d o ~ not exceed 1.0air change I~er hour. ~ulml~wq l t A t l u r ~ : l n e proposect changes aaaress two important areas of concern. First, in 3-8.4, the limit of X of 480 is incorrect, being the value only for metric units. Second, numerous questions have been raised concerning the applicability of the equations in these sections. In many cases, the questions indicate a lack of understanding of the basis or applicability of the equations in these sections. Thus, these changes are needed to clarify the applicability of the equations so that users may properly interpret the results. The clarification included in basedon a letter to the editor of Fire Technology by Heskestad (May, 1991).

28


The equations in these two sections are important for the estima- tion of the time to response of ceiling-mounted spot detectors, which may be used to activate the smoke management system. Without the proper changes, users will not be able to appreciate the assumptions used to formulate these expressions. Consequently, the equations may be misapplied, leading to inappropriate design assumptions. COMMITTEE ACTION: Accept.

(Log #CP11) 9213- 21 - (3-5): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Insert a new section, renumbering all subsequent sections.

3-5* Hazardous Conditions. Hazardous conditions may be deemed to occur as a result of unacceptable temperatures, smoke obscuration or toxic species concentrations (e.g., CO, HCI, HCN) in a smoke layer. Equations to calculate the smoke layer depth, average tern perature rise, optical density and species concentrations during the smoke filling stage and the quasi-steady vented stage are ~rovided in Table 3-5. These equations apply for fire with constant

eat release rates and t-square fires. They may also be used to calculate the conditions within the smoke layer once the vented conditions exists.

The concept of this document are based on maintaining the smoke layer interface level by extracting smoke from the smoke layer in a vented scenario. Prior to the exhaust system operation and for a period of time after its initial operation, there is a smoke filling scenario during which the smoke layer interface level used in the venting calculations may be within the smoke layer.

SUBSTANTIATION: This new section provides equations to conduct analysis of properties of the smoke layer, as part of analysis

ACTION: Accept.

(Log #CP12) 92B- 22 - (3-5.2.1, 3-5.2.2 and 3-5.2.4 (New)): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise 3-5.2.1 and 3-5.2.2 and add a new 3- 5.2.4 as follows:

3-5.2.1 Steady Fires. For steady fires, the height of the initial indications of smoke above the fire surface, z, can be estimated for any time, t, from Equation (9) (where calculations yielding z/H> 1.0 mean that the smoke layer has not yet begun to descend):

z/H = 0.67 - 0 .28 In [(tQI/3/H4/S)/(A/H 2'] (9)

where z = height of the first indications of smoke above t he fire surface

(ft) H = ceiling height above the fire surface (ft) t = time (s)

Table 5-5 Equations for Calculating Properties of Smoke Layer

Smoke FiUin}{ Stage

Parameter Steady Fires T-squared Fires

AT exp(Qn/Qo ) - 1 exp(Qn/Qo ) - 1 (1-X 1) Qc/(poCp V)

n (nmQt)/[ XaAH cA(H'z) ] (nm ct t 3/3) [ XaAH cA(H-z) ] DmQ/( XaAH c V)

t~Qt [po Xadd-I cA(H-z) ] fi*~x3/[3poXaZ~d-I cA(H-z) ]

Vented Stage

fiQ/(poXaatt cv)

where:

Q n = I(1-xi) Qfd t

for s teady fires: Q n = (1-xl)Qt _ for t-square fires: Q n =(1-xi)a'c3/3

Qo = pocpYoA(H-z)

Xa, AH c a n d D m ( com bus t i on efficiency, h e a t of c o m b u s t i o n a n d mass opt ical density) are p rope r t i e s of the fuel

D = opt ical densi ty

Yi = Gas c o n c e n t r a t i o n

H = cei l ing h e i g h t (ft)

fi = Yield fac tor

A = cross-sectional a rea of space (ft 2)

z = smoke layer in te r face pos i t ion (ft)

t = t ime f r o m ign i t ion (s)

29

NFPA 92B-- A95 ROP

Q = heat release rate form steady fire (Btu/s) A = cross-sectional area of the space being filled with smoke (ft2) Equation (9) is based on experimental data from investigations ^

using uniform cross-sectional areas with respect to height with A/HX ratios in the range from 0.9 to 14 and for values of z / H >_ 0.2 [7, 10, 12, 13, 14]. This equation is for the worst case condition, a fire away from any walls. The equation provides a conservative estimate of hazard because z relates to the height where there is a first indication of smoke, rather than the smoke layer interface position.

3-5.2.2 Unsteady Fires. The descent of the height of the initial indications of smoke can also be estimated for certain types of unsteady fires, e.g., t-square fires. From basic theory and limited experimental evidence, the height of the initial indications of the smoke above the fire surface, z, can be estimated for a given time according to the following relation (where calculations yielding z / H > 1.0 mean that the smoke layer has not yet begun to descend):

(lo)

(t and tg in s, H in ft, A in ft2 ; as previously defined) EquatiOn (10) is based on experimental data from investigations

with A /H2 ratios in the range f rom 1.0 to 2~ and for values of z / H >_ 0.2 [10]. Equation (10) is based upon uniform cross-sectional areas with respect to height. This equation is for the worst case condition, a fire away from anywalls. The equation also provides a conservative estimate of hazard because z relates to the height where there is a first indication of smoke, rather than the smoke layer interface position.

3-5.2.4 Varying Cross-Sectional Geometries and Complex Geometries. Equations (9) and (10) are based upon experiments conducted in uniform cross-sectional areas. In practice, it is recognized that spaces being evaluated will not always exhibit a simple uniform geometry. The descent of a smoke layer in varying cross-sections or complex geometr ic spaces may be affected by conditions such as sloped ceilings, variations in cross-sectional areas of the space, and projections into the rising plume. When such irregularities occur, o ther methods of analysis should be considered. Other methods of analysis which vary in their complexity, but may be useful in dealing with complex and non-uniform geometries are:

(a) Scale Models- (see 3-1.1 and 3-1.2) (b) Field Models - (see 3-1.1) (c) Zone Model Adaptation - A zone model (see Section 3-1)

predicated on smoke filling a uniform cross-sectional geometry is modified to recognize the changing cross-sectional areas of a space (see 3-1.1). The ent ra inment source may be modified to account for expected increases or decreases in ent ra inment due to geometric considerations, such as projections.

(d) Sensitivity Analysis -An irregular space is evaluated using equations (9) and (10) at and between the limits of a maximum height and minimum height identifiable from the geometry of the

~pi~ using equivalent height or volume considerations. TANTIATION: The proposal includes clarifications based on

a letter to the editor of Fire Technology by Heskestad [May, 1991]. The essence of these changes is to clarify the applicability of equations (9) and (10), especially relative to the definition of z. In

~ articular, users may treat the smoke layer interface position and the eight, z, as being interchangeable. Given that z relates to the first

indication of smoke, the smoke immediately above that position is not generally expected to pose a significant threat. Consequently, application of the equations to formulate a design based on these equations may be overly conservative if z is misinterpreted to refer to the smoke layer interface position.

In addition, the changes identify the limitations of the equations, specifically that the equations should not be used for z / H < 0.2, e.g., for conditions where the first indication of smoke is approaching the floor of the space. Many of the questions which have been raised concerning the validity of these equations have focused on counter- intuitive results for situations where z / H < 0.2. Given that no data is available for z / H < 0.2, these concerns can nei ther be verified or refuted.

The proposed modification to the definition of smoke layer interface is needed as part of the suggested changes for section 3-5.2, relating to the application of equations (9) and 00 ) . The change to the definition will assist in distinguishing between the smoke layer interface and the first indication of smoke.

The new section 3-5.2.4 provides commentary on geometr ic issues. COMMITTEE ACTION: Accept.

(Log #CP13) 92B- 23 - (3-6): Accept SUBMITTER: Technical Committee on Smoke Management S y s t e l - f l t s , RECOMMENDATION: Add the following to the end of the existing PTaragrap h: . .

he exhaust fan inlets should be sized and distributed m the space to be exhausted to minimize the likelihood of air beneath the smoke layer from being drawn through the layer, sometimes referred to as "plugging." To accomplish this, the velocity of the exhaust inlet should no t exceed a value to cause fresh air to be drawn into the smoke layer. SUBSTANTIATION: Added clarification to discuss the proper location of exhaust outlets. COMMIaTEE ACTION: Accept.

(Log #CP14) 92B- 24 - (3-6.1.2): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Change equation (15) to:

m = 0.0208 Qc 3/5 z [z -< ZL] (15)

SUBSTANTIATION: To correct an error in the limit. COMMITrEE ACTION: Accept.

(Log #CP15) 92B- 25 - (3-6.2): Accept SUBMI'Iq'ER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add the following as noted by underlining:

3-6.2 Balcony Spill Plumes 3-6.2.1 A balcony spill plume is one that flows under and around a

balcony before rising, giving the impression of spilling f rom the balcony (from an inverted perspective) (see Figure 3-6.2). with balcony shill t~lumes involve smoke rising above a f r e . reaching a ceiling, balcony or other simaificant horizor~tal t)roiection, then = travelin~ horizofitaUv towar@the edge of the "bafcofi¢'. Characteris- tics of Me resulting lyalconv st)ill Dlu-me det)end on characteristics of the fire. width of t~e st)ill r)lu~ne.'height ot~the ceiling above the fire. In addition, the oath 6f h~rizontal travel from the plume centerline to the balconv edge is significant.

For situatiorls in~olvin~a fire in a communicat ing st)ace, immediately adjacent to the atrium, air ent ra inment intoVba)cony spill plu/nes'can be calculated from Equation (17):

m = 0.12 (QW2)1 / 3 (Zb + 0.25H) where m = mass flow rate in plume (lb/s) Q = heat release rate of the fire (Btu/s) W = width of the plume as it spills under the balcony (ft) Zb = height above the balcony (ft) H = height of balcony above fuel (ft)

Equation (17) is based on Law's interpretation [16] of small-scale experiments by Morgan and Marshall [17]. Equation (17) should be regarded as an approximation to a complicated problem.

96.2.2 When zh is ant)roximarelv 13 times the width, the balconv shill plume is exS"ected ~o have t h e s a m e t)roduction rate a# an a3dsvinmewic olfime. Consoauenfly, for ;h >13W. the smoke oro/tuction rate from a balco'nv shill t)lurn~ should be estimated hsing eouation (14L " " " _ 3-6_2.5" The width of the plume, W, can be estimated by consider- ing the presence of any physical barriers protruding below the balcony to restrict horizontal smoke migration under the balcony. In the absence of any barriers, visual observations of the width of the balconv spill t)lume at the balconv edge were made in a set of small- scale ext)~ri~ents bv Morgan and Marshall 1171 and analyzed by Law [161. Ir~ these ext)ei'imen~ts, the fire was in a communicating space. immediately adjacent to the atrium. An eouivalent width can b¢ defined by eouating the entra inment f rom'an unconfined balcQny shill nlume to that i'rom a confined balcony spill t)lum¢, The e'uuivalent width is evaluated using the follox~ing'exnression:

W = w + b

where w is the width of the onening from the area of o r ion and b is the distance from the ot)eni~g to t~e balconv edge. - v

30

NFPA 92B-- A95 ROP

Zb

W

Side Front

SUBSTANTIATION: Original equation (17) was very conservative. The original equation attempted to provide reasonable agreement with experimental data over a large range of heights. Instead, the committee believes that this new relationship provides a good estimate for relatively short heights until the plume acts similar to that from an axisymmetric plume. At these tall heights, an improved approach is to use the axisymmetric plume equation. In addition, a task group in the UKfor CIBSE has recommended this equation. Being that researchers in the UK were involved in the experimental work and analysis, the task group considers this group to be the "experts" and should accept their recommendations.

In 3-6.2.3 additional comments are included to provide information on the width of spill plume in the absence o f barriers. Figure 3- 6.2 has been changed to correct an error in labeling of H. COMMYVrEE ACTION: Accept.

(Log #CP17) 92B- 27 - (?-7): Accept SUBMITTEI~ Technical Committee on Smoke Management Systems, RECOMMENDATION: Delete the crossed through language:

?.7 Influence of Plume Contact with Walls. As a plume rises, it also widens. The plume may contact all of the walls of the open space prior to reaching the ceiling. In this case, the smoke interface will be considered to be at the height of contact with all of the surround-

~i~,~ ie~,li:.Z ,,~" C~,t/.~t. The overall plume diameter can be estimated ~ L

SUBSTANTIATIOn: Redundant and confusing. COMMIq['rEE ACTION: Accept.

(Log #CP16) 92B- 26 - (3-6.3.1, 3-6.3.2): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add the following at the end of 3-6.3.1

This assumes that the heat release is limited by the air supply to the compartment, the fuelgeneration is limited by the air supply, and excess fuel burns outside the compartment using air entrained outside the compartment. The methods in this section are also only valid for compartments having a single ventilation opening. Add the following to the e n d o f 3-6.3.2 The virtual source height is determined as the height of a fire

source in the open which gives the same entrainment as the window plume at the window plume flame tip. Further entrainment above the flame tip is assumed to be the same as for a fire in the open. While this development is a reasonably formulated model for window plume entrainment, there are no data available to validate its use. As such the accuracy of the model is unknown. SUBSTANTIATION: Expanded discussion to describe basis of equations (18) through (21). COMMITTEE ACTION: Accept.

(Log #CP18) 92B- 28 - (3-9): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Change equations (24a) and (24b) to read:

AT = (1 - XL ) Qc / (mc) (24a)

AT = 60 (1 -XL ) Q c / ( p cV) (24b)

where

AT = temperature rise of smoke layer (°F) Q.c = convective portion of heat release rate (Btu/sec) m = mass exhaust rate (lb/s) V = volumetric venting rate (cfm) c = specific heat of smoke at smoke layer temperature (Btu/Ib-°F) p = density of smoke at smoke layer temperature (Ib/ft:5 ) XL = heat loss fraction (use ¢ if unknown)

SUBSTANTIATION: To account for heat loss fraction influence. COMMITrEE ACTION: Accept.

31

N F P A 9 2 B - - A 9 5 R O P

(Log #11) 92B- 29 - (4-2): Reject SUBMrFrER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: Figures 4-4.5.1 and 4-4.5.2 show a Type K thermocouple on the diagram of the housing of the motor that drives the exhaust fan. The actual temperature of the motor housing should be displayed in the Fire Fighters' Smoke-Control Station at all times.

Insert a f te r . . . " there may be instances where the direct effects of the fire will be on the equipment," SUBSTANTIATION: COMMITIT.E ACTION: Reject. COMMITrEE STATEMENT: Not appropriate to the scope of NFPA 92B.

(Log #12) 9215- 30 - (4-4.5): Reject SUBMITIXR= Frederick D. Browne, Cambridge, MA RECOMMENDATION: Figures 4-4.5.1 shows an example of measurements that might be seen before the fan is activated and Figure 4-4.5.2 shows an example of measurements that might be seen after the fan is activated for periodic testing.

Insert a f t e r . . . ' o r equivalent sensors that respond to loss of operating power, problems in the power or control circuit wiring, airflow restrictions, and failure of the belt, shaft coupling, or motor itself."

l IqlA~ ~ MIMJS

ims~ ILl, P~, ot P~ for s ~ se~sds to nmd @ @ @

m I PlftUl8 11 m S

G G ~ lma/a ltt. it2. m' It8 fro. s f ~ seemala to mini

SUBSTANTIATION: This proposal ensures that instrumentation will be available to enable the fire department to exercise adequate supervision of the smoke management system in the event of a fire. COMMITI'EE ACTION: R~ect` COMMITTEE STATEMENT: Not appropiate to the scope of NFPA 92B.

(Log #13) 9213- $1 - (5-2.3): Reject SUBMITTER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: The voltages, amperages, and resistances that are printed on monitor panels in the Fire Fighters' Smoke- Control Station should be based on these components tests, if there are no major differences between operational data and design parameters developed in Section 2-3. Major differences should be resolved under Section 5-3.

Insert af ter . . ." including such items as speed, volume, sensitivity calibration, voltage, and amperage." SUBSTANTIATION: Thisproposal ensures that accurate information will be available to the fire department in the event of a fire, COMMITTEE ACTION: Reject. COMMITI'EE STATEMENT: See Committee Action on Proposal 92B-3 (Log #6).

( Log #14) 92B- $2 - (5-3.7): Reject SUBMITTER: Frederick D. Browne, Cambridge, MA RECOMMENDATION: The voltages, amperages, and resistances displayed in the Fire Fighters' Smoke-Control Station during acceptance testing should be included in this documentation.

Insert after . . .~This document should be available for reference for eriodic testing and maintenance."

STANTIATION: This proposal ensures that accurate information will be available for those people who are responsible for

eriodic testing and maintenance. OMMITrEE ACTION: Reject.

$2

NFPA 9 2 B - - A95 R O P

COMMrlTEE STATEMENT: See Committee Action on Proposal 92B-3 (Log #O).

(Log #I 5) 92B- 33 - (5-4.3): Reject SUBMI'I'I~R: Frederick D. Browne, Cambridge, MA RECOMMENDATION: The voltages, amperages, and resistances displayed in the Fire Fighters' Smoke-control Station during the semiannual testing should be included in the operations and maintenance log.

Insert af ter . . . 'q 'es ts should also be conducted under standby power, if applicable." SUBSTANTIATION: This proposal ensures that an)' significant changes in voltages, amperages, and resistances will be noticed by knowledgeablepersonnel during the semiannual testing. COMMII"rEE ACTION: Reject. COMMITI'EE STATEMENT: See Committee Action on Proposal 92B-3 (Log #6).

(Log#4) 9213- 34 - (6-1.1): Accept in Principle SUBMII~T.R: Joseph A. Drouin, Gardner, MA RECOMMENDATION: Delete "NFPA 71, Standard for the Installation, Maintenance, and Use of Protective Signaling Systems." Replace "NFPA 72, Standard for the Installation, Maintenance, and

Use of Protective Signaling Systems" with "NFPA 72, National Fire Alarm Code." SUBSTANTIATION: NFPA 71,72E, and 72H have been incorporated into the NFPA 72-1993, National Fire Alarm Code. COMMFITEE ACTION:_Accept in Principle.

Delete NFPA 71, NFPA 72E and NFPA 72H from 6-1.1. Add "NFPA 72, National Fire Alarm Code" to 6-1.1. In 24.2.1 replace reference to NFPA 72E with reference to NFPA

72, National Fire Alarm Code. In 5-2.4 replace reference to NFPA 72H with reference to NFPA 72,

National Fire Alarm Code. COMMITrEE STATEMENT: Committee Action should satisfy submitter's intent

(Log #CP19) 92B- 35 - (A-3-1.1.3): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add new Appendix material as follows: A-3-1.1.3 Common simplifications of Zone Models are listed in

Table A-3-1.1.3(a). Verifying computer fire model results is important because it is

sometimes easier to obtain results than to determine the results' accuracy. Computer fire model results have been verified over a limited range of experimental conditions [42, 43, 44]; review of these results shouldprovide the user with a level of confidence. However, because the very nature of a fire model's utility is to serve as a tool for investigating unknown conditions, there will be conditions for which any model has yet to be verified. It is for these conditions that the user should have some assistance in judging the model's accuracy. There are three areas of understanding that greatly aid accurate

fire modeling of unverified conditions. T h e first area involves understanding what items are being modeled. The second area involves appropriately wanslating the real-world items into fire model input. The third area involves understanding the model conversion of input to output. The items the modeler must accurately characterize are the fuel,

the compartment, and the ambient conditions, as indicated in Table A-3-1.1.3(b). The fuel heat release rate is an important feature to describe. There are many other details of the fuel that also effect fire growth, such as species production, radiative heat loss fraction, fuel-to-air combustion ratio, and heat of combustion. However, the desired accuracy of the answer dictates which of these should be included and which can be ignored. Compartment vent descriptions must also be properly evaluated. Often, leakage areas can account for substantial, unanticipated gas flows, especially in instances of extreme weather conditions with regard to temperature or wind.

Translating actual characteristics into a format recognizable as model input is the second major area of fire modeling. Some items simply do not merit attention because of their lower-order effects. Other items must be represented in ways that are altered somewhat. An example of the first case is exduding a mechanical ventilation

duct when a large door to a room remains open. An example to the second case is a fire burning along a 5 foot vertical section of wall. The height of the fire is best described as the floor level, the lowest point where flames may entrain air.

The last area of understanding is perhaps the most difficult for the novice to master; this pertains to understanding how the model converts input to output. It is not practical for the new user to grasp every detai[ of this transformation process, but it is possible for the novice to anticipate many results with a basic comprehension of fire dynamics [39, 40] and working knowledge of the three conservation laws [41 ]. The conservation laws can be expressed with differential equations to reproduce the smooth, continuons changes exhibited by properties behaving in real fires. To the degree that the mathematics deviate from the differential representation of the conservation laws, the more uncertain the model accuracy becomes outside the range of verification. The potential for model inaccu- racy is affected by the relative influence of the particular term in the equation. Terms having the greatest influence contain variables that are raised to exponential powers greater than one. Algebraic correlations, other fire models, scale models and

common sense can be used to verify model accuracy. The algebraic equations are only verified given the experimental conditions from which they were correlated. Projections beyond these experimental domains can be based on trends at the experimental endpoints. Using one model to verify another model insures precision, but not necessarily accuracy unless the second model was independendy verified.

Experimental scale models can always be used to verify computer model results. Reduced scale models are the most economical; trends are easily obtainable from such measurements but refined data less readily so.

Table A-3-1.1.3(a) Simplifications in Zone Models

Fuel

Plumes

heat release rate isn't accelerated by heat feedback from smoke layer post-flashover heat release rate is weakly understood and its unique simulation is attempted by only a few models CO production is simulated, but its mechanism is not fully understood through the flashover transition some models do not consider burning of excess pyrolyzate on exit from a vent

plume mass entrainment is +/- 90% and not well verified in tall compartments no transport time from the fire elevation to the position of interest in the plume and ceiling jet spill plume models are not well developed not all plume models consider the fuel area geometry entrainment along stairwells is not simulated entrainment from horizontal vents is not simulated by all models

Layers

hot stagnation layers at the ceiling are not simulated uniform in temperature

Heat Transfer

some models do not distinguish between thermally - thin and thermally-thick walls no heat transfer via barriers from room to room momentum effects neglected

Ventilation

mixing at vents is correlationally determined

33

NFPA 92B-- A95 ROP

Table A-8-1.1.8(b)

Burning Fuel Description

heat release rate as it changes with t ime fire elevation radiat ion fraction species p roduc t ion rate area of fire (line, pool, or gaseous)

Compar tmen t Description

he ight of ceiling size, location and dynamic status (open or closed) of the vent ( including leakage area) thermophysical proper t ies of wall, ceiling and floor material location, capacity and status of mechanical ventilation presence of beams or trusses smoke t ranspor t t ime in the p lume or ceiling j e t structural failure initial t empera tu re

Ambien t Condit ions Description

• elevation * ambien t pressure • ambien t t empera ture • wind speed and direct ion * relative humidi ty * outside tempera ture

SUBSTANTIATION: Explanation offire model's limitations. COMMITTEE ACTION: Accept.

(Log #CP20) 92B- 36 - (A-3-1.2): Accept SUBMITTER: Technical Committee on Smoke Management S~tems, RECOMMENDATION: Revise as follows: A-3-1.2.1 A more complete review of scaling techniques and

examples can be found]n the literature [35]. Smoke flow studies have been made by Heskestad [361 and Quintiere, McCaffrey and Kashiwagi [37]. Analog techniques using a water and salt-water system are also available [38]. Smoke flow modeling for buildings is based on maintaining a balance between the buoyancy and convective "forces" while ignoring viscous and heat conduction effects. Neglecting these terms is not valid near solid boundaries. Some comlJensation can be made in the scale model by selecting different materials of construction.

A-3-1.2.2 Dimensionless groups can be formulated for a situation involving a heat source representing a fire along with exhaust and make-upair supply fans o f a given volumetric flow rate (see Figure 3- 1.2.4). The solution of the gas temperature (T), velocity (v), pressure (p) , surface temperature (Ts) expressed in dimensionless terms and as a function o~x, y, z, and time (t) are:

P !

T

To

V

v ' g l

__.E_P Pogl

Ts

To

: f { x y z t } " 1 ' ' 1 ' ' ] ' - ' l ' I I ' I ]2 ' I ' I3

where I is a characteristic length, g is gravitational acceleration, To is ambient temperature, and ro is ambient density. P1 , P2, and P$ are dimensionless groups arising from the energy release of the fire, fan flows and wall heat transfer.

Q fire e n e r g y rl 1 - - 5/2

poCpToVg 1 flow energy

where Qis the energy release rate of the fire and Cp is the specific heat of the ambient air. where Vfan is the volumetric flow rate of the exhaust fan.

I I 2 = m Vfa n fan flow

V ~ I 5/2 b u o y a n t flow

o.v c o. ea ran r (kpc)w wall h e a t t r ans f e r

where (kpC)w are the thermal properties (conductivity, density and specific heat) of the wall, }x is the gas viscosity and k is the gas thermal conductivity.

The expression of P3 is applicable to a thermally, thick construction material. Additional dimensionless terms (P s) are needed if wall thickness and radiation effects are significant. P3 attempts to correct for heat loss at the boundary by permitting a different construction material in the scale model in order to maintain a balance for the heat losses.

For a typical building, the recommended minimum geometric scaling should be 1/8.

The scaling expression for the fire heat release rate follows from preserving P1 - Similarly, expressions for the volumetric exhaust rate and wall thermal properties are obtained from preserving P2 and P3 • The wall properties condition is easily met by selecting a construction material that is noncombustible and closely matches (kpc)w with a material of sufficient thickness to maintain the thermally-thick condition. SUBSTANTIATION: Added for clarification. COMMITTEE ACTION: Accept.

(Log #CP21) 9215- 37 - (A-3-3.2.2): Accept SUBMITTER= Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise text as follows: A-3-3.2.2 Tables 3-2 and 3-3 list excess gas temperatures at the time of

sprinkler actuation for steady and unsteady (t-square) fires [48]. The tables assume a sprinkler temperature ratin~ of near 165°F (74°C) and a conduction parameter (C) of 1.8 f t ' l / 2 / s e c l / 2 (1 m l / 2 / ~ 1 / 2 ).

The tables are based on the following response equation for heat- responsive dements of sprinklers [8]:

d(ATe) _ u 1/2 d t RTI [ATg - (1 + C/u 1/9) ATe] (A-l)

where ATe = temperature rise (from ambient) of heat-responsive element t ffi time u = gas velocity at sprinkler site AT~ = gas temperature rise (from ambient) at sprinkler site RT~= response time index of sprinkler ( t u I / 2 , where t is the

sprinkler ume constant) C = conduction parameter of sprinkler, representing heat loss by

conduction to the sprinkler mount from the heat responsive element.

34

NFPA 92B-- A95 ROP

Gas temperatures for steady fires were taken from equat ion (3), and gas temperatures for t-square fires were taken f rom equat ion (4). Gas velocities were evaluated from a relat ion between gas velocity and gas tempera ture rise [9] (valid for r / H _'e 0.3):

u / [ ( A T s / T ~ ) g i l l v2 = 0 .59 ( r /H) - ° m (A-2)

where

Too = ambien t air temperature l~ffi acceleration of gravity

= ceiling height (above combustibles) r = radius f rom fire axis

Since the sprinkler response informat ion in Tables 3-2 and 3-3 relates to representative behavior in the r / H range 0 - 0.6, equat ion (2) was evaluated for r / H = 0.3 and normal ambient conditions:

u = 0.23 [aTg HI 1 / 2 (A-3)

where u is in m/s , ATg in °C, and H in m.

The various cases in Tables 3-2 and 3-3 were solved by approximat- ing the t ime-temperature curves using l inear segments. For a t ime segment of l inear rate of rise in gas temperature, d T g / d t = b, the solution to equat ion (A-l) is:

= 13 RTI u - I/u ATe (1 +Cu_l=,)[t - (1 +Cu-I~) ( 1 - e x p ( - t / (RTI u-J@(l-Cu-V~)))]

(A-4)

where ATe and t are measured from the beginning of the segment. The velocity, u, was evaluated f rom equat ion (A-3) at a representative value for ATg in the segment. The total rise in e lement tempera ture dur ing a segment was the rise at the end of the preceding segment, plus the rise calculated in the cur ren t segment, using equation (A-4). The calculations cont inued until the e lement tempera ture rise reached the actuation value (74 - 20 = 54°C), at which time the excess of the gas tempera ture above the actuation value of the hea t responsive e lement was calculated, to be entered in Tables 3-2 and 3-3.

For the steady fires (Table 3-2), detailed calc~l?otions were made 1 / ~ ' I e u r i o k according to this procedure, using values of u "n q a " n (~4 )

equal to the average of the values at the beginning and the end of each segment.

For the unsteady fires (Table 3-3), a somewhat simplified approach was employed because of the magni tude of the task, taking advantage of the fact that the rate of rise in g~ . t empera tu re changes only slowly with time, be ingpropor t iona l to ~1/3. A constant rate of rise was assumed, adopt ing the value existing at the m o m e n t the gas tempera ture was equal to the sprinkler tempera ture rating. Fur thermore, the gas velocity was assumed constant at the value corresponding to this gas temperature, using equat ion (A-3). Hence, the calculations were approximate, but they were considered adequate in view of o ther uncertainties. The values in the upper left-hand corner in Table 3-3 (for t~ = 50 s; RTI = 54,180,630; H = 13 ft) are quite high, for which one might quest ion the applicability of the approximate method. These cases were recalculated, employing a n u m b e r of l inear segments in each case; the results were within 1°C of those listed by the al0proximate method. SUBSTANTIATION: To c'lfirify and present background information. C O M M I T r E E ACTION: Accep t

(Log #CP22) 92B- 38 - (A-3-5 (New)): Accept

• SUBMITrER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add new appendix material as follows:

A-3-5 For des ignpurposes , the topic of algebraic equations for gas concentra t ions andobscu ra t i on of visibility can be addressed for two limit cases:

• Th e smoke filling scenario, where all products of combust ion are assumed to accumulate in the descending smoke layer.

* The quasi-steadyvented scenario, where a quasi-steady balance exists between the rates of inflow into and outflow from the smoke layer.

Normally, the quasi-steady vented scenario is of interest for design purposes because this scenario represents the quasi-steady conditions that will develop with a smoke extraction system operating. The smoke filling scenario may be of interest to analyze the conditions that may develop before the smoke extraction system is actuated. A transient per iod exists between these two limit cases. Dur ing this t ransient intermediate period, the smoke layer is both filling and being exhausted. Analysis of this t ransient per iod generally requires numerical computer-based approaches. From a design standpoint, this per iod should be of little consequence since it is no t a limit case, so it is not addressed further.

Methods to analyze the gas composi t ion and optical characteristics for the two limit cases can be addressed in terms of a n u m b e r of algebraic equations. These algebraic equations are exact, but the data used in these equations are uncer ta in [57]. The user should be made aware of these uncertainties to the extent they are known.

SMOKE FILLING STAGE - OPTICAL PROPERTIES ANALYSIS The average optical density of the descending smoke layer can be

estimated if the mass optical density of the fuel can be reasonably estimated. Equation A-5 is used to estimate the optical density as a funct ion of the mass optical density, the mass of fuel released and the volume of the smoke layer.

t Dmf ~ dt

D(t) D m m f 0 - Vu = Azu(t) ( a - 5 )

where

Dm = mass optical density ( f t 2 / lb ) (m2/kg) mf= mass burn ing rate ( lb/s) (kg/s)2 2 A = cross-sectional area of a t r ium ( f t ) ( m ) Z u = depth of upper layer (ft) (.m) ° V u = volume of upper layer (fro) (m o)

For the case of a flat ceiling, negligible plume area and a fire with constant mass and heat release rates, Equation A-5 evaluates as:

+ 2 t ] -3/21-1 D ( t ) = ×aAHcAu H

(A-6)

is a t i m e c o n s t a n t e v a l u a t e d as

V A H A H

Vent kv(~/3H5/3 kv(°tntn) I/sHS/3

where Q = heat release rate f rom fire (Btu/s) (kW) AH c = heat of combustion (Btu/Ib) (kJ/kg) Hr= height of ceiling above floor (ft) (m) X a = combust ion efficiency

For the case of a flat ceiling, negligible p lume area and a t-square fire, Equation A-5 ewaluates as:

D ( t ) - 3XaAHcAu H D m ~ t 3 { [ 2k at/zt~/~H2/Zl-3/~ } - * 1 - 1 + v 5Au ]] (A-7)

where ct = fire growth rate = 1000/( t~)2, (see)

o

35


For other scenarios, appropriate values must be substituted into Equation A-5. For some scenarios, numerical integration may be necessary.

SMOKE FILLING STAGE-LAYER COMPOSITION ANALYSIS

Analysis of the composition of the smoke layer is analogous in many respects to the analysis of the optical density of the layer. To analyze the smoke layer composition as a function of time, a yield factor fi must first be assigned for each specie i of interest:

gni = fixhf (A-8)

where fi = yield factor (lbproduct/Ibfuei) (kgproduct/kgfuel)

The mass fraction Yi, of each species in the smoke layer is:

where

= mi

1

(A-9)

Yi = mass fraction (lbspede/lbtotal) (kgspede/kgtotal)

The term in the numerator of Equation A-9 is calculated, similar to Equation A-5, as:

t t t

mi = f Iilidt Qf :ffimfdt=ffi y A[-[

o o o , ~ - - - c dt (A-10 )

For the case of a constant yield factor and a t-square fire growth rate, Equation AdO evaluates as:

t a t 2 f i a t 3

mi = f ; f X - - - a ~ c d t - gxaAnc 0

(A-1 l )

For the case of a constant yield factor and a steady fire, Equation A- 10 evaluates as:

t _f~Qs t m i = I f i Qf d t

XaAHc XaAHc 0

(A-12)

The term in the denominator of Equation A-9 represents the total mass of the smoke layer. Typically, the mass of fuel released is negligible compared to the mass of air entrained into the smoke layer, so the total mass of the smoke layer can be approximated as:

~mi = i~V. (A-13) PoToVu

i

For the case where the temperature rise of the smoke layer is small relative to the ambient absolute temperature (i.e., T /T o - 1), Equation A-1S reduces to:

~ m i =poVu (A-14)

i

Substituting Equations A-11 and A-14 into Equation A-9 yields, for the t-square fire:

f i a t 3

Yi = 3PoVuXaAHc (A-15)

Substituting Equations A-12 and A-14 into Equation A-9 yields, for the steady fire:

Vi - f iQct (A- 16) PoVuXaAHc

For a fire that grows as a t-square t'we from Q = o at time t = o t~o Q ,= ~ s at time t = has, then continues to burn indefinitely at ~ = tJ..q s. EquAtions A-15 anti A-16 can be combined to yield:

Yi - fi[at~tJ3 +Qis (t - tqs)] (A-17)

PoVuXaAHc

The volume of the smoke layer, Vu, in these equations is evaluated by the methods presented in Section $-6 with V u = A (H - z).

QUASI-STEADY VENTILATED STAGE - OPTICAL PROPERTIES ANALYSIS

Under quasi-steady ventilated conditions, a balance exists between the rate of mass inflow into the smoke layer and the rate of mass outflow from the smoke layer. The average optical density of the smoke layer can be calculated on a rate basis as:

Dmfilf DmQf D -

Vexh XaAHcVexh (A-18)

Equation A-18 can be used to determine the average optical density of the smoke layer for a given exhaust rate. Alternatively, the required exhaust rate needed to produce a particular optical density, D, can be determined by rearranging Equation A-18 as:

~rex h - DmQf DXaAHc

(ADO)

Use of Eqations A-I 8 and A-19 requires knowledge of the mass optical density, Dm, of the smoke.Mass optical densities for a variety of fuels are reported by Tewarson (1988) and by Mulholand (1988). Values reported by these investigators are based on small- scale fire tests, generally conducted under well-ventilated conditions.

~6


It should be recognized that the optical properties of smoke can be affected by ventilation so it is not clear how well these small-scale data correlate with large-scale behavior, particularly for scenarios where the large-scale conditions include under-ventilated fires. This topic requires further research.

QUASI-STEADY VENTILATED STAGE- LAYER COMPOSITION ANALYSIS

The mass fraction of each species i in the smoke layer under quasi- steady flow conditions is given in general by:

r~ Yi = ~ - -~ .

i

(A-20)

Under quasi-steady flow conditions, the mass flow rate of each species is given as:

rili =firiay =fi Qf XaAHc

(A-21)

The total mass flow rate under quasi-steady conditions is given by:.

lhi ~'~ ~'~xla = PoWent = PoCQexh - ~rexp) (A-22) i

Substituting Equations A-21 and A-22 into Equation A-20 permits calculation of the mass fraction for each species i of interest in terms of a known exhaust rate:

Yi - Yi,o = fiQf (A-23) po×.anc(~xh - X~xp)

To determine the required volumetric exhaust rate needed to limit the mass fraction of some species i to a limit value, Yi, Equation A-23 is rearranged to:

fiQy (A-24) "V'exh ='~rexp + PoXaAHc(Yi - Yi,o)

The volumetric expansion rate, ~rexp, is calculated as:

Vexp O~ (1 - x l ) ~

pocpTo PoCpTo (A-25)

SUBSTANTIATION: For clarification. COMMr['rEE ACTION: Accept.

(Log #CP23) 92B- 39 - (A-3-5.2): Accept $UBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add verbiage to read: A-3-5.2 Equations (9) and (10) are empirically-based equations for

estimatingthe smoke layer interface position during the smoke filling process. This review of equations (9) and (10) is divided into two parts:

• comparison of the results of both equations (9) and (10) with those frbm theoretically based equations (with empirically determined constants, hereafter referred to as ASET-based equations.

• evaluate the predictive capability of equation (9) and an ASET- based equation by comparing the output from the equations with experimental data.

1. Comparisons with ASET-hased equations Comparisons of the NFPA 92B equations for smoke filling with

ASET-based equations provide an indication of the differenkes between empirically based equations, e.g., equations (9) and (10), with those that are based principally upon theory.

Steady Fires A theoretically-based equation for smoke filling can be derived

using the laws of conservation of mass and energy to determine the additional volume being supplied to the upper layer [57]. Using Zukoski's plume entrainment correlation [58]:

z/H = [ 1 + 2kv(tQVS/H4/3)13/2 3(A/H ~)

(A-26)

where z = smoke layer interface position (m) H = ceiling height (m) t = time from ignition (s) Q= heat realease rate (kW) A = cross-sectional area of space (m 2) k v = entrainment constant ~ 0.064 m2t/3/(s-kW 1/$)

A comparison o f z /H predicted by equations (9) and (A-26) is

~ resented in Fi~ure A-3-5.2.1 for a ceilin~t height of 30 m, a steady re size of 5 M ~ a n d awide range of A/~12 ratios. In general, the

agreement between the two equations is reasonable. Equation (9) oredicts a lower smoke layer interface position at most times, exceot In the case of the voluminous space represented byA/H2 ofl0. ltn this case, equation (9) indicates a delay of approximately 100 s before a layer forms, while equation (A-26) iridicates immediate e formation of the layer. Such a delay is reasonable for such a larg space. This delay can could be addressed by including an additional term in equation (A-26) to account for the transport lag [49]. The transport lag is estimated as 37 s for this case with a height of 30 m and cross-sectional area of 9,000 m2. While the comparison in Figure A-3-5.2.1 is useful, it only applies to

selected values of A, H and Q. This comparison can be generalized for all values of A, H and Q by forming a ratio of the two equations expressed in terms of t.

teqn A-I _

teqn9 k(Z) exp 0 . ~

Figure A-3-5.2.2 indicates the relationship of the time ratio with the normalized smoke layer depth, (H - z)/H. Forperfect agreement between the two equations, the time ratio should have a value of 1.0. However, the time ratio varies appreciably. The dme ratio is within 20% of 1.0 only for a very small range. For normalized smoke layer depths less than 0.13 (or a normalized clear height of 0.87), equation (A-26) always predicts a shorter time to reach a particular depth than equation (9). Conversely, equation (9) predicts shorter times to attain any normalized smoke layer depth in excess of 0.13.

The time ratio is relatively insensitive for values of (H - z ) /H ranging from 0.4 to 0.6. Within this range, the time ratio is nominally 1.5, i.e., the time predicted by equation (A-2fi) to obtain a smoke layer of a particular depth is 50% greater than that predicted by equation (9). Alternatively, equation (9)predicts a more rapid descent to this range of smoke layer depths than equation (A-26).

37

N F P A 9 2 B - - A 9 5 R O P

T-square Fires A similar comparison of the empirically-based equation (10) and a

theoretically-based equation for t-square fires can be conducted. The ASET-based equation is:

20kv ts/s H-4/s ] -an z/H = [ 1 + - - -

t~Wa 2 J (A-27)

where:

~ : fire growth rate (s) comparison of the predicted z /H values are presented in Figure

A-$-5.2.3for a ceiling height of $0 m, a moderate fire growth rate (t~ = 300 s) and a wide range o fA]H 2 ratios. For values of A/H2 up to ~ 1.0, the agreement appears very reasonable once the smoke layer has formed. Again, the empirically derived eauation implidtly includes the transport lag. For A/H2 of 10.0, the 2~elay for a smoke layer to form is greater than that for smaller A / H ratios such that reasonable agreement in smoke layer interface position is not achieved until approximately 800 s. The estimated transport lag is 206 s [49]. The value of z /H of 0.59 for the point of intersection of the various

curves for the two equations is a constant, independent of the values for A, H and Q. Thus, for values of z / H > 0.59, equation (A-27) estimates a shorter time to attain a particular position of the smoke layer interface, where equation (10)estimates a faster time for lesser values o fz /H.

Given the different exponents on the right side of the two equations, a~eneral comparison is again only possible by solving for the times anti expressing a ratio.

Z 2/3 _

teqn A-2 _ ( '91) -'69 1) .6

teqnl 0 4kv 6 ( Z ) -'69

The relationship of the time ratio for various normalized smoke layer depths (H - z ) /H is provided in Figure A-3-5.2.4. In general, the agreement between the two predicted times for t-square fires is much better than that for steady fires, with the predicted time using equation (A-27) being within 20 percent of that from equation (10) for (H - z ) /H values from 0.26 to 0.80. As in the case of the steady fire, the time ratio is less than 1.0 for small normalized smoke layer depths. However, in this case, the time ratio does not exceed 1.0 until the normalized smoke layer depth is at least 0.40.

2. Large-scale Experimental Programs in Tall Ceiling Spaces The predictive capabilities of each equation can be examined by

comparing their output to experimental data. The predictive capability of equation (A-26) is examined by

comparing the output to large scale experimental data. Sources of the experimental data involving a range of ceiling heights from 2.4 to 12.5 m as well as room sizes and fire scenarios are identified in Table A-3-5.2. Included in the table are the data sources referenced in the initial development of equation (9) of NFPA 92B [50]. Two additional sets of experimental data have become available since the committee's initial analysis [51,52]. Comprehensive descriptions of the test programs are provided elsewhere [54-57|. Because the two additional sets of data were collected from fires in spaces with significantly greater ceiling heights than in the initial sets of data, the new sets of data are of particular interest.

The measured and predicted smoke layer positions as a function of time from the previous and two new sets of data are presented in Figure A-3-5.2.5. The data identified as ~The Committee's" includes all of the data upon which the committee based initial development of equation (9). The new sets of data are identified separately. As indicated in the figure, the smoke layer position from the data analyzed is between that measured by NRCC and BRI. Thus, despite the differences in ceiling height, the new and initial sets of data appear to be reasonably similar. The graph labeled as "NFPA 92B" depicts the predictions of equation (9). In general, agreement between the predictions from both equations (9) and (A-26) and the experimental data is very reasonable. Equation (9) provides a lower limit of the experimental data, including the new NRCC data. Equation (A-26) appears to predict a mid-range value of the data.

Equations comparable to equations (9) and (A-26) can be derived for variable cross-sectional areas and for fires which follow a power law, e.g., t-square fires. In addition, algebraic equations pertaining to a variety of smoke layer characteristics are available, including temperature, light obscuration and species concentration [57].- These equations are applicable to evaluating transient conditions prior to operation of the smoke management system or equilibrium conditionsd with an operational smoke management syste-m. Thus, a variety of algebraic equations are available and can serve as useful tools for relatively elementary designs or as checks of specific aspects of computer calculations for more complicated situations.

Table A-3-5.2 Summary of Full Scale Experiments

Research Fuel Heat Release Dimension Measurements of Group Rate of Test Room Smoke Layer Position

New Data

Visual observations, BRI [51] Methanol pool, 1.3 MW 30 x 24 m, first temperature

3.24 m 2 (steady) height: 26.3 m rise

NRCC [52]

Committee Data

Ethanol pool, 3.6 m diameter 8 m¢ ( s t y , 1

55 x 33 m, height 12.5 m

First temperature i rise

Sandia, Test 7 [10]

Propylene Burner, 0.91 m diameter 516kW

Mullholhnd [54] Acetylene Burner 16.2 kW

Cooper [55]

Hagghnd [561

Methane burner

Kerosene pool, 0.5 m square

25,100, 225 kW

280 kW

18.3 x 12.2 m, height 6.1 m 3.7x 3.7 m, height: 2.4 m

89.6 m 2 room, corridorand lobby height: 2.4m

5.62 x 5.62 m, height: 6.15 m

First temperature rise, carbon dioxide concentration Temperature rise, light obscuration

Temperature rise

V~ual observations, first temperature rise

$8

N F P A 9 2 B - - A 9 5 R O P

Comparison o[ aloebraJc equations Eqn 9 & A-1: s teady fire

I • I [ " . . "~

6 I I . - , ,, Height: 30 m =: 0 . 8 - I ~ t. " k ~ . ' ' - ~ ~ NO vendng ---...::: . . . . . . . . . . . . • " . . . . . . . . . . . . . . . . :

... "8o.a- I \ ~ \ " • . • 0 . 2 - ~ x ~ " . . . . . . . . .

. . . . . . . . .

I I I I 0 100 2 0 0 3 0 0 4 0 0 5 0 0

Time (s~c) floo

Eqn 9, A/H2.0.5 ~ - Eqn 9./v1-1z=1.0 . . . . Eqn 9,/sJI-12=I0.

Eqn A-I , A/H2,,.0.5 • - - Eqn A-I, /V'H2=I.0 . . . . Eqn A-I, FJH2=I0.

Fga,re A,3-S.~.]

Eqn 9 & A- I : steady lice

I :: J

0.6

0.4

°: 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.1)

NormaJized smoke layer depth (H-z)M

Figure A-$-5.2.2

comoeriam o~ akjeen~ eq.aUom I=qn 10 & A-2: t-lKIoere fire

1.6

1.4

!:i O2.

0 I I I I I I I I I

0 0.1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 Normalized smoke layer depth (H-z)M

F'~m-e A-3-5.2.4

ComlXUlaon ol smoke layer I:.x~on E x p ~ i m e r d ~ data ca ~ l o m

• " 7

. . . . . . . . . . . .

I I I I I l I I 0 0.1 0 .2 0 .3 0.4 o.s 0 .6 o.7 o.e

(IQ'n/H'C~(A/H~( kW' n~m ~ }

I 0.9

4. BRI x NRC C [ ] Committee's data

NFPA 92B - - Eqn A-25

Figure A-3-5.2.5

1

o . 9 -

0.8 -

0 . 5 - -

:~0.2 -

J°, o-

Comparison of ~ equdorm Eqn 10 & A-2: I-oqufe fwe

V I ~ . . . . . ", ~ : 3 o m

' \ ~ . . . °'" . " ~ .

\ ~ ' . .

~ ° " ° ° ° ° . • . . . .

I I I I I I I I 100 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0

Time (see)

~ E q n l 0 , A / H 2 , , 0 . 5 ~ ~ EqnI0,APHS,,1.0 . . . . Eqs~10.A/I.P,10.

~ Eqn A-2, ~ . 5 . . . . Eqn A.2, A~12,1.0 . . . . Eqn A-2, A4-1¢,10.

lrgure A-3-5.2.3

SUBSTANTIATION: For clarification. COMMITI'EE ACTION: Accept.

(Log #CP24) 92B- 40 - (A-3-5.2.4): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add new paragraph as follows: A-3-5.2.4 In the absence of an analysis usin~ scale models, field

models, or zone model adaptation, a sensitivity analysis should be considered. A sensitivity analysis can provide important information to assist in engineering judgments regarding the use of Equations (9) and (I0) for complex and non-uniform geome~-ies. An example of a sensitivity analysis is illustrated as follows for a large space hawng a non-flat ceiling geometry.

First step of the analysis would be to convert a non-uniform geometry to a similar or volume-equivalent uniform geometry.

In the case of the geometry shown in Figure A-3-5.2.4.1, this would be done as follows: - Convert the actual non-rectangular vertical cross-section area to a

rectangular vertical cross-section of e.gual area. - The height dimension corresponding to the equivalent rectangu-

lar cross-section would then be used as a substitute height factor Hsub in Equation (10).

39

NFPA 92B-- A9S ROP

To evaluate the appropriateness of the resulting geometry, the results of Equation (10) should be compared with other minimum and maximum conditions as indicated by Figure A-5-5.2.4.2. An appropriate method of comparison could be a graph of

Equation (10) as shown in Figure A-3-5.2.4.3. Assume that the building in question can be evacuated in three minutes and that the design criteria requires the smoke layer to remain available 10 feet above the floor at this time. A review of the curves would indicate that the smoke layer heights as calculated for the substitute case is appropriate. This conclusion may be drawn by noting that neither tile extreme minimum height case (H = 30 ft, W = 60) or the maximum height case (H = 60 ft) offer an expected answer, but the results for two cases (H = 41.6, W = 60; and H = 30, W = 83.3) can be judged to reasonably approximate the behavior of the non-uniform space. It may otherwise be unreasonable to expect the behavior indicated by the maximum or minimum cases.

10'

10'

L 20' .LIOLLIU'_L 2u" _ r r 7 - 7- - I - "7

A = W X H 7 0 0 = 6 0 X H H = 11 .66 H sus = 30 +

F.

. I t

11.66=41.7

60.0' --

RESULTING SUBSTITUTE CROSS SECTION

lrtgm'e A-3-5.2.4.1

f u J - - - - 1

I I

F'~ure A-3-5.2.4.2

I 'll-" H=3Q.W-IIO "4-- H-I~W,IIO -)1(- H-41.S.W=(IO I "E~ H-I~I.W=41.1S "X-- H-~.W-II33 I

Figure A-5-2.4.$ Comparison Data for Guidance on Non-t~ctangular Geometries-growlng F'tre.

SUBSTANTIATION: Proposed example helps to clarify methodoi- 0 .

~ g ~ ~ ACTION: Accept.

40

N F P A 9 2 B - - A 9 5 R O P

(Log #CP25) 92B- 41 - (A-3-6): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add new Section A-3-6 to read: I A-3-6. Limiting the size and distribution of the exhaust fan inlets is I

intended to prevent the smoke from cooling before it can be exhausted by keeping the layer up near the ceiling. This is particularly important for spaces where the length is greater than the height, such as shopping malls.

Fan inlets should be distributed because a high exhaust rate at any one point in thin layers could cause fresh air from below the smoke layer to be drawn through the layer, creating the reverse situation of a bathtub drain. The objective of distributing the fan inlets is therefore to establish a gentle and a generally uniform exhaust rate over the entire smoke layer. [ SUBSTANTIATION: Clarification. COMMI'IWEE ACTION: Accept

(Log #CP26) 92B- 42 - (A-3-6.2.1): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Add appendix paragraph to read: A-3-6.2.1 Agreement oft_he predictions from equation (17) with

those from small-scale experimental efforts ispresented in Figure A- 3-6.2. Whereas the agreement is quite good, the results are only from two small-scale experimental programs.

0 . 6

O

0.4

o

(OL~)'= J • 0 . 2 B a l c o n y depth

0 oz5 , ~ - - ' ~ - • o.5o

0 ~ J ~ ~ I ~ ' ~ ~ i ' ' ~ ~ I o 0 . 5 1 .0 1 .5

Xv

lrtgure A-3-6.2 [17,61]

SUBSTANTIATION: Clarification. COMMITrEE ACTION: Accept

(Log #CP29) 92B- 43 - (Appendix D): Accept SUBMIT'r~Ra Technical Committee on Smoke Management Systems, RECOMMENDATION: Add new entry under NBSIR88-3695 as follows:

NISTIR 4833 Peak Heat Release FIJ¢[ Gommoditv Rate (kW) Computer Work Station 1,000 - i,300

SUBSTANTIATION: New research results. COMMITrEE ACTION: Accept.

(Log #CP3O) 9213- 44 - (Appendix D): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Replace Equation 17 with:

m o = 0.36 (QW~)1/3 (Zb + 0.25H) SUI~TANTIATION: For metric conversion. COMMIT£EE ACTION: Accept

(Log #CP31) 92B- 45 - (Appendix D): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Delete the example 1 (b). SUBSTANTIATION: Assumption is outside of the limits of Equation (3). COMMITrEE ACTION: Accept

(Log #CP27) 92B- 46 - (Appendix E): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Revise the text of Appendix E, Problem 1.

The last portion of (a) starting with the words "Determine t:" should be deleted and the following inserted in its place:

Since X = 24,804 falls outside the limits of 3-3.4, solve for t using X = 480 to determine the minimum sprinkler operating time:

X = t Q 1 / 3 / H 4 / 3 480 = t (5000) 1/3 / (120)4 /3 480 = t (17.1)/591.9 t = 16,614 sec or 277 rain

SUBSTANTIATION: In the example, the value of X is calculated as 24,804 which yields a sprinkler activation time of 855,000 seconds or 14,250 minutes as compared to a smoke detector activation time of 8.6 minutes. Paragraph 3-3.4 of the Guide limits the value of X to 480 based on experimental data. The value of 480 would yield a sprinkler activauon time of 16,614 seconds or 277 minutes. Thus, there would be a considerable period of time prior to sprinkler activation during which the smoke management system would be expected to maintain tenable conditions. It may not be the 855,000 seconds used in the example, but it would certainly exceed the 277 minutes calculated using X = 480.

The purpose of TIA 91-1 on NFPA 9gB - 1991 was to correct the example. It retains the value of having the example in the Appendix while i/lusa'adng the point that there can be a considerable length of time between activation of the smoke detection system and the

9orinklers. MMITrEE ACTION: Accept.

(Log #CP28) 92B- 47- (Appendix G): Accept SUBMITTER: Technical Committee on Smoke Management Systems, RECOMMENDATION: Appendix G Add references: 26. Heskestad, G. and Delichatsios, M.A., "Update: The Initial

Convective Flow in Fire," Fire SafayJourna~ 15, p.471 (1989) 27. Newman,J.S. and Hill, J.P., "~ssessment of Exposure Fire

Hazard to Cable Trays," NP-1675 Research Project 1165-1-1, Prepared for Electric Power Research Institute by Factory Mutual Research Corporation, January, 1981.

28. Sako, s. and Hasemi, Y., "Response Time of Automatic Sprinklers Below a Confined Ceiling," Fire Safety Science - Proceed- in~s of the Second International Svmoosium. Hemisphere Publishing Corporation, NewYorl~, 1§89, p. 613,

29. Heskestad, G. and HilI,J.P., "Experimental Fire in Multiroom/ Corridor Enclosures, FMRCJ.I. 0J2N8.RU, Factory Mutual Research Corporation, October, 1985.

30. Mulhoiland, G, Handa, T., Sugawa, O., andYamamoto, H., "Smoke Filling in an Enclosure," Fire Science and Technology LIA p. 1 (1981).

31. Hinkley, P.L., Hansell, G.O., Marshall, N.R., and Harrison, R., "Experiments at the Multifunctioneel Training centrum, Ghent, on the Interaction Between Sprinklers and Smoke Venting," Building Research Establishment Report, 1992.

32. Yamana, T. and Tanaka, T., "Smoke Control in Large Scale Spaces," Fire Science and Technology._. 5, p. 41 (1985).

33. Walton, W.D. and Notorianni, "A Comparison of Ceiling Jet Temperatures Measured in an Aircraft Hangar Test Fire with

41


Temperatures Predicted by the DETECT and LAVENT Computer Models," NISTIR (Draft), Building and Fire Research Laboratory, National Institute of Standards and Technology, August, 1992.

34. Purser, D.A., "ToxicityAssessment of Combustion Products," SFPEHandbook of Fire Protection Engine~ring, . QuincF. NFPA, 1988.

35. Quintiere,J.G., Fire Safetvl. 15, 1989. 36. Heskestad, G., "Determin~.tJon of Gas Venting Geometry and

Capacity of Air Pollution Control System at Factory Mutual Research Center", FMRC Ser. No. 20581, Fire Mutual Research Corp., Norwood, MA, Nov. 1979.

37. Quintiere,J,G.,McCaffrey, B.J., and Kashwagi, T., Comb. Sci. and Technov.. 18, 1978.

38. Steclde'r, ILD., Baum, HAL, and Quintiere,J.G., 21st Sympo- sium (Int.) on Combustion.. 1986, pp. 143-149.

39. diNenno, P.J. edt. SFPE Handbool¢ of Fire Protection Engineming, National Fire Protection Association, Quincy, MA 02269, 1990.

40. Drysdale, D.D. "An Introduction of Fire Dynamics,"John Wiley & Sons, New York, 1985.

41. Welty, J.R., Wicks, C.E., Wilson, ILE., "Fundamentals of Momentum, Heat and Mass Transfer,"John Wiley & Sons, New York, 1976. 42. Peacock, R.D., Davis, S., Babrauskas, V., "Data for Room Fire

Model Comparisons", Journal of the National Institutue of Standards and Technology, Vol. 96, (4)July 1991.

43. Soderbom, J., "Smoke Spread Experiments in large Rooms. Experimental Results and Numerical Simulations," Statens Provningsanstalt, SR Report 1992:52, Swedish National Testing and Research Institute, Boras, Sweden 1992.

44. Emmons, H., "The Use of Fire Test Data in Fire Models," The Home Fire Project Technical Report No. 78, Harvard University, Division of Applied Sciences, February 1989.

45. Thomas, P.H., Heselden,J.M., and Law, M., "Fully-Developed Compartment Fires - Two Kinds of Behavior, "Fire Research Technical Paper No. 18,

46. Gottuls, D., Roby, 1L, and Eglo, C., "A study of Carbon Monoxide and Smoke Yields from Comparmaent Fires with External Burning; 24th Symposium (International) on Combustion, the Combustion Institute, 1992, pp. 1729-1735.

47. Builen, M.C., and Thomas, P.A, "Compartment Fires with Non- Cellulosic Fuels; 17th Symposium (International) on Combustion, The Combustion Institute, 1979, pp.1139-1148.

48. *Heskestad, G. "Letter to the Editor ,"Fire Technol%rv, 272, May 1991, pg. 174-185.

49. Mowrer, F.W. andWilliamson, R.B., "Estimating Room Temperatures from Fires along Walls and in Comers," Fire Technol- ogy, 25,2, May 1987, 133-145. 50. Heskestad, G., "Letter to the Editor," Fire Technology, 27, 2, May

1991, 174-185. 51. Yamaha, T., and Tanaka, T. "Smoke Control in Large Scale

Spaces (Part 2: Smoke Control in Large Scale Spaces (Part 2: Smoke control Experiments in a Large Scale Space)", Fire Science and Technology, Vol. 5 No. 1, 1985, 41-54. 52. Personal communication, G.D. Lougheed, National Research

Council of Canada, March 20, 1991. 53. Nowlen, S.P., "Enclosure Environment Characterization

Testin~ for the Base Line Validation of Computer Fire Simulation Codes,' NUREG/CR-4681, SAND 86-1296, Sandia National Laboratories, March 1987. ,,54. G. Mullholland, T. Handa, O. Sugawa and H. Yamamoto, Smoke Filling in an Enclosure," Paper 81-HT-8, ASME, 1981. 55. L.Y. Cooper, M. Harkelroad,J. Quintiere andW. Rinkinen, "An

Experimental Study of Upper Hot Layer Stratification in Full-Scale Multiroom Fire Scenarios," Paper 81-H%9, ASME, 1981.

56. Hagglund, B.,Jannson, R. and Nireus, K., 'Smoke Filling Experiments in a 6x6x6 Meter Enclosure," FOA Rapport C20585-06, Forsvarets Forkingsanstalt, Sweden, September 1985.

57. Milke, J.A., and Mowrer, F.W., "An Algorithm for the Design Analysis of Atrium Smoke Management Systems," FP93-04, Depart- ment of Fire Protection Engineenng, University of Maryland at College Park, May 1993.

58. Zokoski, E.E., Kubota, T., and Cetegen, B. 1980/1981, "Entrainment in Fire Plumes", Fire Safety J, 3, 1980/1981, pp. 107- 121. 59. j. s. Turner, Buoyancy Effects in Fluids, Cambridge University

Press, Cambridge (1973). 60. D. Spratt and A.J.M. Heselden, "Efficient Extraction of Smoke

from a Thin Layer Under a Ceiling," UKJoint Fire Research Organization Fire Research Note No. 1001 (1994).

61. Hanseli, G.O., Morgan, H., and Marshall, N.R., "Smoke Flow E~esriments in a Model Atrium", BRE Occasional Paper, July 1993.

TANTIATION: Proposed references needed to support changes being made to NFPA 92B. COMMITTEE ACTION: Accept.

42

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