How does alcohol-resistant AFFF foam primarily operate against hydrocarbon fires?

Alcohol-resistant Aqueous Film Forming Foam (AFFF) functions primarily by forming a vapor-suppressing layer, which is critical when combating hydrocarbon fires. This type of foam is specifically designed to extinguish flammable liquid fires, including those involving hydrocarbon-based fuels.

When alcohol-resistant AFFF is applied to the surface of a burning liquid, it spreads quickly to cover the surface and forms a stable film. This film aids in suppressing flammable vapors that contribute to the fire's combustion process. By creating this vapor-suppressing layer, the AFFF limits the amount of oxygen that reaches the fuel, thereby reducing the fire's intensity and ultimately leading to extinguishment.

The effectiveness of this foam in forming a protective layer allows it to specifically address the needs of hydrocarbon fires, as opposed to merely cooling the area or creating a blockade against combustible gases. While cooling and heat absorption are important aspects of fire suppression, the unique function of vapor suppression is what makes alcohol-resistant AFFF especially suitable for hydrocarbon fires.