Foam Fire Extinguishers (Class B)

Foam Fire Extinguishers are designed for use primarily on flammable liquids and secondly paper/wood fires.

Foam extinguishers have a nozzle that creates foam. It is called an aspirating nozzle and the jet of foam solution through the nozzle entrains air that is mixed in the outlet tube so producing foam. The foam fire extinguishers are located in the dangerous goods store.

Foam Fire Extinguishers are constructed of a powder coated, lined steel or a stainless steel cylinder with a brass valve. The extinguishing medium is a solution of water and 3% Aqueous Film Forming Foam (AFFF) or 6% Polar Solvent Foam which is under pressure from a nitrogen charge.

Standard AFFF is used on hydrocarbon fire such as petrol and oil. Polar solvent foam is used on alcohol and isopropyl alcohol. The alcohol will draw out the water from standard foam but the Polar foam produces a barrier between the alcohol and the foam so allowing the foam to smother the fire.

Foam Fire Extinguishers must NOT be used on electrically charged fires, as the extinguishing medium is conductive and its use can result in an electric shock.

Foam Fire Extinguishers must always be recharged after use as the quantity of the extinguishing medium and the amount of nitrogen charge has been reduced. The gauge on the head may show that the extinguisher has some charge left, but the amount left in the extinguisher will not be equal to the rating on the cylinder. Also the valve may leak and the extinguisher will be empty if it is required to use it again.