Fire fighting foam systems suppress fire by separating the fuel from the air (oxygen). Depending on the type of foam system, this is done in several ways:
Foam blankets the fuel surface smothering the fire
The fuel is cooled by the water content of the foam
The foam blanket suppresses the release of flammable vapors that can mix with the air
Uses & Applications
Foam systems are generally used in applications where flammable liquids are present. Typical applications include fuel storage tanks areas, petrochemical plants, aircraft hangars and facilities that store flammable or volatile liquids. The foam not only contains extinguishing agents to put out the fire but also acts as a "blanket" to exclude oxygen "feeding" the fire and to provide vapor suppression so protecting against re-ignition.
There are various types of foam available from a basic protein foam through to Aqueous Film Forming Foam (AFFF) and Film Forming Flouroprotein (FFFP) with alcohol resistant foam used for polar solvents.
Foam-extinguishing systems shall be installed, maintained, periodically inspected and tested in accordance with NFPA 11, NFPA 11A and NFPA 16 and their listing.
Foam-extinguishing systems shall be inspected and tested at intervals in accordance with NFPA 25.