Why is AFFF used for hydrocarbon fuel fires?

• A. It floats due to lower specific gravity.
• B. It forms a vapor-suppressing film due to low viscosity.
• C. It is common at military installations.
• D. All of the above.

Answer: (D)

AFFF is effective for hydrocarbon fires because it provides both surface cooling and vapor suppression, and it spreads and blankets the fuel quickly. Its density is lower than most hydrocarbon fuels, so when applied it rides on the surface instead of sinking, allowing the water component to absorb heat and slow the flame. It also forms a thin, durable film over the fuel thanks to film-forming agents, and its low viscosity lets that film spread rapidly to cover the surface, suppressing vapor release and reducing the chance of re-ignition. The widespread use at military installations reflects a standard, well-established approach to quickly and effectively control hydrocarbon fires. Taken together, these properties explain why AFFF is chosen for hydrocarbon fuels.