Which material is primarily used in AFFF foam for firefighting?

Aqueous Film Forming Foam (AFFF) is specifically designed for fighting flammable liquid fires, particularly those involving petroleum products and certain solvents. The primary component of AFFF foam is water, as it serves as the main solvent for the foam concentrate. The formulation combines water with various chemicals to create a foam that can effectively blanket and smother fires, preventing the release of flammable vapors and cooling the surface.

When used, the foam forms a thin film on the surface of the burning liquid, which helps to extinguish the fire more efficiently than plain water would. While other materials like alcohol-resistant agents and surfactants are also important in foam formulations, water remains the critical base that allows the foam to be effective in firefighting operations.

In contrast, carbon dioxide is effective for certain classes of fires but does not provide the same smothering and cooling effect as AFFF. Alcohol, while potentially flammable, is not a key constituent of AFFF, and petroleum is the type of material the foam is designed to combat, rather than a component of it.