Which extinguishing agent is used for Class B fires?

• A. Water
• B. AQUEOUS Film-Forming Foam (AFFF)
• C. CO2
• D. PKP

Answer: (B)

Class B fires involve flammable liquids, so the best extinguishing approach is one that blankets the liquid surface, cools it, and prevents vapors from continuing to burn. Aqueous Film-Forming Foam creates a durable foam layer that floats on the liquid, forming a film that separates fuel from air and cools the surface. This combination stops vapor release and suppresses the fire on liquid spills or runways, making it particularly effective for hydrocarbon fires.

Water alone tends to spread flammable liquids, which can spread the fire rather than suppress it. CO2 can blanket a confined space by displacing oxygen, but it doesn’t cool or spread a foam-like barrier over the liquid surface, so vapors can persist and re-ignite. PKP powder can knock down some fires, but it leaves residue, can obscure visibility, and isn’t as effective at continuous vapor suppression for liquid spills as foam.