Which type of fire requires special extinguishing agents such as foam?

Class B fires involve flammable liquids and gases, such as gasoline, oil, paint, and solvents. These materials can produce vapors that ignite and create a hazardous fire situation. Foam extinguishing agents are particularly effective for combating Class B fires because they can smother the flames, prevent evaporation of the flammable liquid, and create a barrier that inhibits re-ignition.

Foam acts by forming a layer over the burning surface, cutting off the oxygen supply and cooling the material underneath. This makes it distinct from the other classes of fires, which have different extinguishing requirements. Class A fires, involving ordinary combustibles like wood or paper, are typically fought with water or dry chemical agents. Class C fires involve electrical equipment and require agents that do not conduct electricity, often dry chemical or carbon dioxide extinguishers. Class D fires are fueled by combustible metals and require special agents designed to smother the reaction rather than using water or foam, which could exacerbate the situation. Thus, foam is essential for effectively managing Class B fires due to the unique properties and hazards associated with flammable liquids.