Which specific type of firefighting foam is specifically formulated and most effective for extinguishing large-scale spill fires involving polar solvents like alcohol?

The specific type of firefighting foam specifically formulated and most effective for extinguishing large-scale spill fires involving polar solvents like alcohol is Alcohol-Resistant Aqueous Film-Forming Foam, commonly abbreviated as AR-AFFF. Polar solvents, such as various types of alcohol, are liquids that readily mix with water, meaning they are soluble in water. This property presents a unique challenge for fire suppression because conventional foams, like standard Aqueous Film-Forming Foam (AFFF), rely on an aqueous film and a foam blanket that would be rapidly dissolved and destroyed by the polar solvent’s water-miscible nature, rendering the foam ineffective. AR-AFFF is uniquely designed to overcome this issue. It contains a special polymer in its concentrate. When AR-AFFF is applied to a polar solvent fire, this polymer precipitates and forms a protective, insoluble polymeric membrane at the interface between the foam solution and the polar solvent. This membrane acts as a crucial physical barrier, preventing the polar solvent from mixing with and dissolving the water content of the foam blanket. Above this protective polymeric membrane, the AR-AFFF then forms a stable, cohesive foam blanket. This foam blanket effectively extinguishes the fire by cooling the fuel surface, separating oxygen from the fuel vapors, and suppressing the release of flammable vapors, thereby achieving rapid and lasting fire extinguishment. This dual action of membrane formation and foam blanket creation makes AR-AFFF the most effective solution for polar solvent fires.