Which of the following types of foam is primarily used for suppressing flammable liquid fires?

Aqueous Film Forming Foam (AFFF) is specifically designed to suppress flammable liquid fires, making it the most suitable choice for this scenario. AFFF works effectively by forming a film that spreads across the surface of the burning liquid, effectively smothering the fire and preventing the release of flammable vapors. This property allows it to be highly effective on hydrocarbon fuels, such as gasoline and diesel, which are common in flammable liquid fires.

While other foam types, such as alcohol-resistant foam, may also be used for specific types of fires involving polar solvents, AFFF is known for its versatility and broad application in various flammable liquid fire scenarios. Dry powder foam is typically used for metal fires or specific situations involving flammable gases but may not be ideal for general flammable liquid fires. Foam concentrate itself is a term used to describe the concentrated liquid version of foam, which requires mixing with water to create an effective firefighting solution but does not inherently indicate the type of foam best suited for flammable liquid fires. Therefore, AFFF stands out as the most effective choice for directly addressing these fire incidents.