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U.S. Postal Service
Fire Extinguishing Equipment. Facilities Handbook.
Postal Service, Washington, DC
Series S-10, August 1970, 29 p.
fire extinguishers | extinguishing | fire hoses | sprinkler systems | carbon dioxide | standpipes | Class A fires | Class B fires | Class C fires
To use fire extinguishing equipment properly, it is imperative to know something about the main kinds of fire. Fires are usually divided into three principal classes: (1) Class A - Fires that start in ordinary material such as paper, wood, cloth, or rubbish. This type of fire can usually be extinguished with water or with multipurpose dry chemical. (2) Class B - Fires involving grease or flammable liquids, such as gasoline, oil, or kerosene, which burn rapidly. These fires are most likely to start in garages, paint shops, spray paint booths, lubrication racks, at gasoline pumps, or in building maintenance shops. They are usually put out by blanketing to exclude air. (3) Class C - Fires that start in electrical equipment such as batteries, battery charges, transformers, generators, and switchboards. Use of water or of a chemical which conducts electricity may result in death or severe injury to persons trying to stop the fire. It is of primary importance to use an extinguishing material which will not conduct an electrical charge.