NRC Report: Advancements and advantages of compressed air foam systems

Fire fighting foam has been in use in the Fire Services for over 75 years. It was originally designed as a surfactant to improve the absorption of water into Class A combustibles such as wood and paper. It quickly found use in fighting flammable liquid spill fires since the foam could float on the surface of the burning fuel and extinguish the fire by sealing off the surface. This separates, the fuel from the flame, absorbs the fuel vapour and prevents thermal feedback to the fuel. As a result, foam concentrates evolved along two lines: AFFF or "Aqueous Film Forming Foams" for Class B or liquid fires and Class A for wildland and structural fires.