Fire Retardant Foam, or fire suppression foam, is a foam used for fire suppression. Its role is to cool the fire and to coat the fuel, preventing its contact with oxygen, resulting in suppression of the combustion. The surfactants used need to produce foam in concentration of less than 1%. (Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids.)

Class B foams are designed for class B fires - flammable liquids. The use of class A foam on a class B fire may yield unexpected results, as class A foams are not designed to contain the explosive vapors produced by flammable liquids. Aqueous film forming foams (AFFF) are water-based, frequently containing sodium alkyl sulfate, and/or perfluoro telomer as surfactants. They have the ability to spread over the surface of hydrocarbon-based liquids. Alcohol-resistant foams (AR-AFFF) contain a polymer that forms a protective layer between the burning surface and the foam, preventing foam breakdown by alcohols in the burning fuel. Alcohol resistant foams should be used in fighting fires of fuels containing oxygenates or fires of liquids based on or containing polar solvents.

Low-expansion foams have an expansion rate less than 20 times. Foams with expansion ratio between 20-200 are medium expansion. Low-expansion foams such as AFFF are low-viscosity, mobile, and able to quickly cover large areas. High-expansion foams have an expansion rate over 200. They are suitable for enclosed spaces such as hangars, where quick filling is needed.

Applications

Every type of foam has its best application. High-expansion foams are used when an enclosed space, such as a basement or hangar, needs to be quickly filled. Low-expansion foams are used on burning spills. AFFF is best for spills of jet fuels, FFFP is better for cases where the burning fuel can form deeper pools, AR-AFFF is suitable for burning alcohols. The most flexibility is achieved by AR-AFFF or AR-FFFP. AR-AFFF must be used in areas where gasolines are blended with oxygenates, since the alcohols prevent the formation of the film between the FFFP foam and the gasoline, breaking down the foam, rendering the FFFP foam virtually useless.

Action Response Team uses this AR-AFFF foam, which is a low expansion foam, allowing us to maximize our output and effectiveness.