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Fire /
Classification of Fires |
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CLASS A fires
occur in ordinary combustible materials such as wood, cloth and paper.
The most commonly used extinguishing agent is water which cools and
quenches. Fires in these materials are also extinguished by special dry
chemicals for use on Class A, B & C fires. These provide a rapid knock
down of flame and form a fire retardant coating which prevents reflash. |
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CLASS B fires
occur in the vapor-air mixture over the surface of flammable liquids
such as grease, gasoline and lubricating oils. A smothering or
combustion inhibiting effect is necessary to extinguish Class B fires.
Dry chemical, foam, vaporizing liquids, carbon dioxide and water fog all
can be used as extinguishing agents depending on the circumstances of
the fire. |
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CLASS C fires
occur in electrical equipment where non-conducting extinguishing agents
must be used. Dry chemical, carbon dioxide, and vaporizing liquids are
suitable. Because foam, water (except as a spray), and water-type
extinguishing agents conduct electricity, their use can kill or injure
the person operating the extinguisher, and severe damage to electrical
equipment can result. |
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CLASS D fires
occur in combustible metals such as magnesium, titanium, zirconium and
sodium. Specialized techniques, extinguishing agents and extinguishing
equipment have been developed to control and extinguish fires of this
type. Normal extinguishing agents generally should not be used on metal
fires as there is danger in most cases of increasing the intensity of
the fire because of a chemical reaction between some extinguishing
agents and the burning metal. |
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