Foam fire extinguishers provide a cleaner and more effective alternative to dry powder extinguishers for class A and B fire risks. Foam fire extinguishers are ideal for multi-risk situations where both Class A combustable materials and Class B flammable liquid risks are likely to be found, or where Class B represents a direct hazard. Foam spray extinguishers are especially suitable for Class B fires involving flammable liquids such as oils, spirits, fats, and certain plastics. The blanketing effect of foam spray gives rapid knockdown which smothers the flame and thus prevents the re-ignition of flammable vapors by sealing the surface of the solution. On Class A fires the foam enhances the cooling ability of the water base. On Class B fires the foam enables the formation of an aqueous film capable of spreading on the surface of burning fuels, which prevents vapor production and seals the surface.