What type of foam is preferably used at a concentration of 3%-6% for gasoline fires?

The preferred choice for dealing with gasoline fires is Aqueous Film Forming Foam (AFFF), which is effective at concentrations of 3%-6%. AFFF is specifically formulated to combat flammable liquid fires, such as those involving gasoline, by forming a film that quickly spreads across the surface of the liquid fuel. This film helps to suppress the release of flammable vapors and enables the foam to provide a rapid and effective barrier between the fuel and the combustion process.

AFFF works by providing both a cooling effect and a vapor sealing effect, making it especially suitable for hydrocarbon fuels like gasoline. The ability to create this film is crucial because gasoline has a low flash point and is highly volatile, which makes it prone to ignition. By applying AFFF at the right concentration, firefighters can effectively control and extinguish the fire.

In contrast, other options such as high expansion foam and alcohol-resistant foam have different applications. High expansion foam is typically used for filling large areas with foam and is more effective in suppressing fires in confined spaces or when dealing with more significant volumes of materials being ignited. Alcohol-resistant foam is specifically designed for polar solvents or alcohols, which behave differently than hydrocarbon-based fuels like gasoline. Class A foam is intended