What type of fire requires foam as an extinguishing agent?

Foam is specifically effective for Class B fires, which involve flammable liquids such as gasoline, oil, and solvents. These types of fires can produce flammable vapors that can spread quickly, making them particularly hazardous. Foam works by creating a barrier that suppresses the release of flammable vapors and cools the burning material. It effectively smothers the fire while preventing re-ignition.

This makes foam an appropriate choice for combating Class B fires, as it not only extinguishes flames but also prevents further ignition. In contrast, Class A fires, which involve ordinary combustibles like wood, require water or other agents that penetrate the material for effective extinguishment. Class C fires, which involve energized electrical equipment, must be approached with non-conductive agents, while Class D fires, which involve combustible metals, often require special dry powder agents. Thus, foam's unique properties make it ideal for handling Class B incidents.