Class B fire

In fire classes, a Class B fire is a fire in flammable liquids or flammable gases, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, or alcohols. For example, propane, natural gas, gasoline and kerosene fires are types of Class B fires. The use of lighter fluid on a charcoal grill, for example, creates a Class B fire. Some plastics are also Class B fire materials.

Class B fires are distinguished from the other fire classes: Class A fires ("ordinary combustibles" such as wood, paper, or rubber); Class C fires (in which the burning material is energized electrical equipment) and Class D fires (in which the burning material is combustible metals). The less-commonly-used Class K (known in Britain as Class F) refers to fires involving cooking oil or fat; in the United States, these materials are part of Class B.

Fires are classified by the proper extinguishing agent. While water is used to fire Class A fires, using water on a class B fire (such as a grease fire) is extremely dangerous. This is because burning grease is hotter that the boiling point of water (212 degrees Fahrenheit or 100 degrees Celsius); when water is placed on grease, it creates steam which expands rapidly and splatters, causing burns and spreading the fire). Because of this, Class A fire extinguishers use water, while Class B fire extinguishers use dry chemicals (foam or powder), such as aqueous film-forming foam, multi-purpose dry chemicals such as ammonium phosphate, and halogenated agents (such as Halon 1301 and Halon 1211). or highly pressurized carbon dioxide. Some fire extinguishers contain chemicals designed to fight both Class A and Class B fires.

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