Aqueous Film Forming Foam is used in which percent concentrations?

• A. 0.1 and 0.5
• B. 3 and 6
• C. 8 and 10
• D. 12 and 15

Answer: (B)

AFFF works by mixing a foam concentrate with water to create a foam solution that blankets and cools the fuel, forming a protective film on hydrocarbon fires. The percent figure in this context is the concentrate-to-water ratio used to make that foam solution. For AFFF, the standard mixing ratios are 3% and 6%. That means you blend 3 parts concentrate with 97 parts water for a 3% mix, or 6 parts concentrate with 94 parts water for a 6% mix. A 3% mix is common for many hydrocarbon fires, while a 6% mix is used for heavier fuels or larger incidents where faster knockdown and a stronger film are beneficial. The other percentages listed aren’t the typical AFFF strengths and wouldn’t provide the expected film-forming performance.