What is the percentage of AFFF foam recommended for a hydrocarbon fire?

The recommended percentage of AFFF (Aqueous Film-Forming Foam) for use on hydrocarbon fires is indeed 3%. AFFF is specifically formulated to be effective on flammable liquid fires, particularly those involving hydrocarbons. The effectiveness of AFFF at this concentration is due to its ability to form a film that spreads over the liquid surface, smothering the fire by both sealing off the liquid from oxygen and preventing the release of flammable vapors.

At the 3% concentration, AFFF has been shown to create a strong, cohesive film that enhances its ability to suppress flames and extinguish the fire quickly and effectively. This is particularly important in situations involving large volumes of flammable liquids, where rapid extinguishment is crucial to prevent further spread and potential explosions.

The other percentages of AFFF would not provide the optimal coverage and firefighting capability needed for hydrocarbon fires, which through empirical testing have demonstrated that 3% is the effective concentration.