ABC dry chemical

[1] ABC dry chemical is usually a mix of monoammonium phosphate and ammonium sulfate, the former being the active component.

Dry chemical powder puts out the fire by coating the burning material with a thin layer of dust, thereby separating the fuel from the oxygen in the air.

Class A fires are caused by the burning of common combustible materials, such as wood, paper, or most plastics.

[4] The powder breaks the chain reaction of liquid and gas fires by coating the surface to which it is applied.

Creosote, which is the by-product of the incomplete burning of wood (typically due to chronic combustion-air insufficiency), is extinguished by the chain reaction caused by the chimney bombs.

When a Class K / Class F extinguisher is not available an ABC dry chemical extinguisher can be carefully used to control a fire involving cooking oils or fats if the operator is aware of the potential need to re-apply more chemical if the oils or fats reignite.

[1] Due to the corrosive properties of ABC dry chemical, it is not recommended for use around aircraft or sensitive equipment.