Foam for fire protection purposes is an aggregate of air-filled bubbles formed from aqueous solutions and is lower density than the lightest flammable liquids. It is principally used to form a coherent floating blanket on flammable and combustible liquid lighter than water and prevents or extinguishes fire by excluding air and cooling the fuel. It also prevents re-ignition by suppressing formation of flammable vapors. It has the property of adhering to surfaces, providing a degree of exposure protection from adjacent fires.
Foam may be used as a fire prevention, control or extinguishments agent for flammable liquid tanks or processing areas. Foam solution for these hazards may be supplied by fixed piped systems or portable foam generating systems. Foam may be applied by foam discharge outlets, which allow it to fall gently on the surface of burning fuel or it may be introduced by other means. Foam may also be applied to these hazards by portable hose streams using foam nozzles, portable towers or large capacity monitor nozzles.