Which statement about AFFF is NOT true?

• A. It helps seal fuel vapors.
• B. It resists breakdown from other chemical agents.
• C. It forms a film that isolates fuel from air.
• D. It is ineffective on aviation fuel fires.

Answer: (D)

AFFF works by creating an aqueous film-forming layer on hydrocarbon fuels, which cools the fuel and blankets the surface so vapors are sealed off and the fuel is blocked from air. This foam also spreads quickly to form a film that isolates the fuel from the air, reducing the chance of re-ignition. The foam is designed to be stable and resist breakdown in the presence of other firefighting agents, helping it stay effective long enough to control the fire. Aviation fuel fires— Jet A and AvGas—are hydrocarbon fires, and AFFF is specifically used for them, so claiming it is ineffective on aviation fuel fires is not true.