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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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