Class B foams are especially effective on which fuels?

• A. Hydrocarbon fuels
• B. Polar solvents
• C. Water-based fuels
• D. Metal fuels

Answer: (A)

Foam for Class B fires is designed for flammable liquids, especially hydrocarbons. It works by spreading a stable film on the liquid surface and forming a foam blanket that cools the fuel, seals the surface, and keeps vapors from escaping into the air. This combination effectively suppresses ignition and helps prevent reignition on hydrocarbon fuels like gasoline, diesel, and kerosene.

Polar solvents don’t respond as well to standard Class B foams because many of them mix with water or require alcohol-resistant foams to maintain a protective film. Water-based fuels aren’t typical flammable liquids that respond to this foam method, and metal fuels aren’t liquids at all and require different, Class D extinguishing agents.