Occupational Safety and Health Administration USA Department of Labor OSHA OUTREACH SAFETY TRAINING Mirdif Security & Safety Consultants CONSTRUCTION INDUSTRY REGULATIONS Subpart F – Fire Protection and Prevention 29 CFR 1926.150 – 29 CFR 1926.155 Introduction: This lecture is discussing in brief: What is fire, classes of fires, different types of fire extinguishers, how to use each type of extinguisher, methods of fire extinction and how to extinguish all classes of fires. The guidance also discusses, fire prevention measures and how to act correctly in case of emergencies. What Is A Fire? Simply fire is a chemical reaction which involves rapid oxidation or burning of a combustible material. In the past, we learned that three elements, fuel, heat, and oxygen were necessary for fire to start and continue burning, hence the fire triangle concept. In recent years this concept has been expanded to include a fourth element, that of chemical reaction, thus creating the fire tetrahedron. 1
Transcript
Occupational Safety and Health Administration USA Department of Labor
OSHA OUTREACH SAFETY TRAINING
Mirdif Security & Safety Consultants
CONSTRUCTION INDUSTRY REGULATIONSSubpart F – Fire Protection and Prevention
29 CFR 1926.150 – 29 CFR 1926.155
Introduction:This lecture is discussing in brief: What is fire, classes of fires, different types of fire extinguishers, how to use each type of extinguisher, methods of fire extinction and how to extinguish all classes of fires.The guidance also discusses, fire prevention measures and how to act correctly in case of emergencies.
What Is A Fire?Simply fire is a chemical reaction which involves rapid oxidation or burning of a combustible material.In the past, we learned that three elements, fuel, heat, and oxygen were necessary for fire to start and continue burning, hence the fire triangle concept.In recent years this concept has been expanded to include a fourth element, that of chemical reaction, thus creating the fire tetrahedron.
Fig. 1 : Fire Tetrahedron
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The following is a brief description of each element and their interaction:1- Fuel (Combustible Substances): Combustible substances exist as Solids, Liquids and gases.
Solids: Such as wood, paper, cartons, cloth.Liquids: Such as M. Gasoline, Solvents, Alcohols.Gases : Such as Propane, Butane, Hydrogen.
2- Oxygen: All combustible substances need oxygen to burn. Oxygen is normally available in the air in sufficient quantities (21%). There must be at least 16% oxygen present for a fire to burn.
All substances (fuel) will only burn in air if the ratio between the air and the vapor of these substances lies between certain limits. If too much, or too little fuel is present, burning will not take place.These limits are referred to as the lower and upper limits of flammability.
3- Heat (Source of Ignition): Heat is the energy needed to increase the fuel's temperature to the point where sufficient vapors are produced for ignition to occur. The source of ignition which can produce enough energy are:
A- Electricity : * Electricity is the most common and costly ignition source of fires and explosions.* How can Electricity Starts a Fire?
- By overloading an outlets.- Faulty installation of wiring (Loose connections).- Damaged wire or cable's insulation.- Electrical malfunction of motors.
B- Smoking: * Fires caused by the misuse of smoking materials (cigarettes) is the second major source of ignition .
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* Many of these fires have been the result of smoking materials dropping into holstered furniture and producing smoky and toxic smoldering fires.
C- Cutting and Welding (Hot Works): Hot works includes brazing, cutting, grinding, welding, soldering,
using torches etc., fires that are ignited by hot work result from sparks or globules of molten metal that generated.
D- Open Flames: Open flames include portable torches, cigarettes, lighters,
matches, space heaters etc.
E- Hot Surfaces: This category includes those instances where heat is carried by
conduction from the surface of electrical heating equip., boilers, furnaces, ovens etc. to adjacent combustibles and causes fires.
F- Spontaneous Ignition: Some materials oxidize and throw off heat. If those materials are
confined, that heat cannot escape, then ignition can result. Some products that heat spontaneously are animal and vegetable
oils , also paint deposits that contain drying oil may spontaneously ignite . Also rags contaminated with oil may ignite spontaneously.
G- Static Sparks: Static electricity occurs between two objects in contacts. Electrical
charges are produced on the objects when they are separated. If these charges build up, it will develop enough energy to jump as a spark to nearby grounded or less highly charged objects.
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These sparks can ignite flammable vapors, flammable gases or finely dispersed combustible solid materials.
H- Friction: Friction generates heat, in machinery, loose or worn moving parts
rubbing against each other can generate enough heat to ignite nearby combustibles.
4-Chemical Reaction: The chemical chain reaction known as fire, occurs when fuel, oxygen,
and heat are present in the right conditions and amounts.
Classes of Fires: Fires are classified by the fuel they burn. There are four classes
according to the American system:
1- Class A Fires:
- These are fires involving ordinary combustibles:- Cloth, wood, paper, rubber, many plastics. - The most effective extinguishing agent is WATER,
and dry chemical rated for A, B, and C fires.
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2- Class B Fires :
- These are fires involving flammable and combustible liquids such as: Motor Gasoline - Solvents (Acetone) - Alcohols.
- Fires that involves energized electrical equipment where the electrical non - conductivity of the extinguishing agent is of great importance.
- The extinguishing agents are: Dry Chemical - Carbon Dioxide - Halons.
- Water or any fire extinguisher contains water or any agent mixed with water are not allowed to be used on fires involving live electrical equipment, since water is a good conductor of electricity.
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1- Class D Fires :
- These are fires involving metals such as: Sodium - Potassium Magnesium.
- Special types of fire extinguishers is used to extinguish such fires
5- Class K Fires:
- It is fires occur in Kitchens grease and oils.,
Fire Extinguishers: There are six types of Fire Extinguishers:
o Water Fire Extinguisherso Foam Fire Extinguisherso Dry Powder Fire Extinguisherso Carbon Dioxide Fire Extinguisherso Halon Fire Extinguisherso Liquid Powder Fire Extinguishers (Kitchen)
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This lecture will explain the following fire extinguishers only:
A- Dry Chemical Fire Extinguishers : Stored - Pressure Dry Chemical Fire Extinguishers :
- This type of fire extinguishers are available in different sizes (3 , 6 & 12 Kgs) and the type of extinguishing agent is (Mono Ammonium Phosphate) which is suitable for class A , class B and class C fires.
- It is advisable to avoid using of dry powder fire extinguishers on fires involving sensitive electrical equipment such as computers, since the powder particles will damage those equipment. Carbon Dioxide or Halon fire extinguishers are advised to be used in this case since they do not leave any residues after use.
B- Carbon Dioxide Fire Extinguishers: - This type of fire extinguishers are available in different sizes (2
kgs - 6 kgs - 10 kgs - 20 kgs - 30 kgs) .- It is used to extinguish class (B) fires (flammable liquids), also it is
very effective on fires involving electrical equipment, since it does not leave any residues after use.
- It extinguish fires by replacing some of the oxygen in the air.
C- Halon Fire Extinguishers : - This type of fire extinguishers (Halon 1211 - BCF) are available in
different sizes (1 kg, 3 kg, 6 kg, 12, kg etc.).- It is used to extinguish class (A) fires and class (B) fires also it is very
effective on fires involving electrical equipment, it is recommended to be used to extinguish fires involving delicate and costly electronic equipment, since it does not leave any residues after use.
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- Halon 1211 (BCF) is discharged as a mixture of vapor and liquid droplets which gives good projection and long throw.
- Halon as (CFC) have impact on the ozone layer (Ozone Depletion) and now new substances have been developed to replace halons such as: FM - 200 & 3M - CFA - 410 .
General Rules For Using Portable Fire Extinguishers:
1- Fight the fires in up wind direction.2- Start fighting the fire from safe distance (2 - 5 m) away from the
flame.3- Direct the stream to the base of the fire.4- Sweep the stream from side to side.5- Do not leave the fire area unless you are sure that the fire is
completely out. If the fire re-ignite, repeat the process.
Fire Prevention Measures:- The best way to fight fires is to prevent them.- The following measures are to be taken into consideration to
help preventing Fires:
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1- Good housekeeping is the key. Trash should always be placed in appropriate containers and emptied daily. Clean work areas are safer than cluttered or dirty one.
2- For those who smoke, smoke only in designated areas and never leave lit cigarettes unattended. Also never smoke in bed.
3- Good storage and handling of materials, specially Flammable materials.* Store all flammable liquids in tightly, closed containers.* Store flammable liquids in areas away from sources of flame,
heat or sparks.* Never smoke around flammable materials.* Dispose of all flammable wastes in covered metal containers.* Only use flammable liquids in well - ventilated areas.
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* Clean up all spills of flammable liquids immediately.
4- To prevent Electrical Fires : Replace damaged cords or plugs. Keep cords away from heat and water. Never run cords under rugs. Always pull an electrical cord from outlet by the plug and never
by the cord. Make sure electrical connections are tight to avoid loose
connections which might lead to sparks. Always use properly rated fuses. Avoid plugging too many cords into an electric outlet. (Avoid
overloading).
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5- Keep heaters away from curtains and furniture, and not to use the heaters on drying clothes.
How to Use a Fire Extinguishers:
PASS
Pull إجذب Aimوجه Squeeze إضغط Sweepحرك
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Distributing Extinguishers:
• Extinguishers should be placed in locations provide easy access and are readily free from temporary blockage.
• Near normal paths of travel, near exits and entrances.• Mounted on walls, the operating instructions must face outwards, and
can be removed easily.• Ext. with gross weight of no more than 40 pounds (18 kgs) should be
installed so that the top of the extinguisher is not more than 5 feet above the floor.
• Ext. more than 40 pounds (except wheeled types) should be installed so that the top of the extinguisher is not more than 3.5 feet from the floor.
• In no case should the clearance between the bottom of the extinguisher and the floor be less than 4 inches.
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