Fire classes

Class C Fires. Class C fires involve electrical equipment. The extinguisliing agents recoiiuiiended are dry chemicals, carbon dioxide, compressed gas, and vaporizing liquid. 

As the gas pressure inside the extinguisher increases, it pushes a jet of water out of the extinguisher s nozzle. Because soda acid extinguishers expel water, they should only be used on class "A" fires. Class "A" fires are those that involve wood, paper, cardboard, and cloth. Soda-acid fire extinguishers should never be used on electrical or grease fires because the water they use can cause these kinds of fires to spread and burn out of control. 

There are various fire classes that require different sprinkler designs. The detailed descriptions of these classes and sprinkler specifications are given in NFPA 13.12 An average chemical plant is classified as an ordinary hazard (Group 3) area. Various sprinkler specifications for this type of area are given in Table 7-7. 

Fires are classified based on the type of fuel involved. Fuels are typically placed into three classes ordinary combustibles (like wood and paper), flammable liquids, and combustible metals. For firefighting, a fourth fire class, electrical fires, is also considered. The four main classifications of fire are shown in Table B-1. 

Fire Class Tests Simulations Time to Flashover to Fire Growth... 

Fire classes and type of extinguishers and use. Fuel, oxygen, and heat. How to extinguish a "flashback. Calling for help and knowing extinguisher locations. 

Because of their favourable cost-performance ratio, polyvinyl chloride (PVC) coated polyester (PET) fabric is the most common basic material used. It can be applied over the whole spectrum from small temporary to wide-span structures. With a top-coat that protects the PVC from soiling and early ageing, a life-span of up to 20-25 years can be obtained. PVC-PET composites are joined by high-frequency or hot wedge welding. With flame-retardant additives to the PVC coating, fire class B1 can be achieved. 

Class C extinguishers are intended for electrical fires, which, because of the potential shock hazard, preclude the use of water. Many class B extinguishers are also rated for use on electrical fires. Class D extinguishers are used primarily for reactive metal fires and a few other specialized applications. Due to the extra cost of these units, only those laboratories which actively use reactive metals need to be equipped with class D units. 

The best way to learn how to use an extinguisher is to practice in a fire class with a firefighter. Many fire departments give free hands-on training to the public and educational institutions. Don t pass up this opportunity to handle an extinguisher. The instructions below are appropriate to read but there is no substitute for hands-on training. 

Electrical fires - fires involving electrical equipment or circuitry do not constitute a fire class on their own, as electricity is a source of ignition that will feed a fire until switched off or isolated. But there are some pieces of equipment that can store, within capacitors, lethal voltages even when isolated. Extinguishers specifically designed for electrical use like carbon dioxide or dry powder should always be used for this type of fire hazard. 

Different methods and equipment are needed for dealing with different types of outbreak. For example, whereas some fires can be extinguished simply with water (fire class A), those occurring in fuel stores (coal, oil, gas) must be tackled only with special powder or carbon dioxide extinguishing agents (fire classes B and C). The same applies to outbreaks in electrical installations. 

Fig. 2a Powder extinguisher, 50kg powder filling (foam compatible), for fire classes B and C, or 50 kg powder filling, for fire classes A, BandC...

Fig.5c Carbon dioxide extinguisher, filled with 6kg of CO2/ with fog nozzle or with tube for CO2 snow, for fire class B...

Fig. 1 a Auto extinguisher with pressure gauge, filled with 2 kg of dry powder extinguishing agent, for fire classes A, B and C... 

Fig. 5a Water (gas pressure) extinguisher, with 10 litres water filling discharged by compressed nitrogen, for fire class A...

BS 7937 2000, Specification for portable extinguishers for use on cooking oil fires (Class F), British Standards Institution, London 2000... 

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