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Fire Extinguishers in the Workplace

Do you know what classes of portable fire extinguishers should be used in your work area? As stated in 1910.157(d)(1), portable fire extinguishers shall be provided for employee use and selected and distributed based on the classes (Class A, Class B, Class C, Class D, and Class K fire extinguishers) of anticipated workplace fires and the size and degree of hazard which would affect their use. The class of fire extinguisher needed to extinguish a fire should always be clarified for persons having the potential to use them.

Class A extinguishers are air-pressurized water extinguishers that are designed for putting out fires pertaining to: wood, paper, cloth, rubber, and certain plastics.

Important! Never use water to extinguish flammable liquid fires. Water may make matters worse by spreading the fire. Never use water to extinguish an electrical fire. Water is a good conductor and use of a Class A extinguisher on this type of fire may lead to electrocution.

Class B extinguishers deliver Carbon Dioxide (CO2), a non-flammable gas that displaces oxygen. This extinguisher shoots pieces of dry ice from the nozzle end. Class B extinguishers put out fires associated to: oils, gasoline, paints, lacquers, greases, solvents, and other flammable liquids.

Important! CO2 extinguishers are not recommended for Class A fires because they may continue to smolder and re-ignite after the CO2 dissipates. Never use CO2 extinguishers in a confined space without first ensuring that employees have the proper respiratory protection. CO2 displaces oxygen!

Class C are dry chemical extinguishers that put out fires by coating the fuel with a thin layer of fire retardant powder, separating the fuel from the oxygen. The powder also works to interrupt the chemical reaction. Dry chemical extinguishers may be marked for multi-purpose use on A, B, and C fires.

Class D portable extinguishers are used against fires of combustible powders, flakes, and shavings from metals such as magnesium, titanium, potassium, and sodium.

Class K extinguishers are dry and wet chemical extinguishers used to extinguish kitchen fires. Because of the higher rate of heat in vegetable oils in commercial cooking appliances, Class K rated extinguishers are required to be installed.

Important! Do not use a Class A extinguisher on a deep fat fryer fire, an explosive reaction may result. In addition, extinguishing agents in many Class K extinguishers are electrically conductive and should only be used after electrical power to kitchen appliances has been shut off.

Where extinguishers are provided but not intended for employee use, the employer is required to have an emergency action plan and fire prevention plan in accordance with the requirements of 29 CFR 1910.38 and 29 CFR 1910.39, respectively. In such cases, only requirements of 1910.157 paragraphs (e) and (f) that outline the inspection, maintenance, and testing apply.