Which firefighting foam is primarily used for Class B fires?

Aqueous Film-Forming Foam (AFFF) is the primary firefighting foam used for Class B fires, which involve flammable liquids such as gasoline, oils, and solvents. AFFF is effective because it forms a film that spreads over the surface of the burning liquid, cutting off the fire's access to oxygen and suppressing vapors that can fuel the fire. This film also helps to extinguish the fire quickly while preventing re-ignition.

The unique formulation of AFFF allows it to be used effectively on both polar and non-polar flammable liquids, making it a versatile choice in various firefighting scenarios involving Class B hazards. Its rapid extinguishing capability and ability to form a protective barrier are key reasons it is the preferred foam in these situations.