Which type of foam can be utilized on both hydrocarbon and water-soluble fuels?

The correct answer is AR-AFFF (Alcohol-Resistant Aqueous Film Forming Foam). This type of foam is specifically formulated to effectively extinguish both hydrocarbon fuels, such as gasoline and oils, as well as polar solvents, which are water-soluble fuels. AR-AFFF achieves this through the incorporation of certain additives that allow it to repel water and form a barrier on the surface of the flammable liquids.

When dealing with hydrocarbon fuels, AR-AFFF forms a cohesive and continuous film that helps to smother the flames and prevent reignition. For water-soluble fuels, which can be challenging to extinguish using standard foams, AR-AFFF creates a blanket that separates the fuel from oxygen and cools the fire to reduce the heat.

The other types of foam mentioned do not have the same capabilities. For instance, alcohol-resistant foam is helpful against polar solvents but does not necessarily have the broad range for both types of fuels as AR-AFFF does. Protein foam is primarily effective on hydrocarbon fires and lacks the formulation necessary to be effective on water-soluble fuels. Foam concentrate is a general term and does not specify a type that has the unique characteristics required to handle both types of fuels effectively. Thus, AR-AFFF