What is the primary function of foam in fire extinguishment?

The primary function of foam in fire extinguishment is to float on liquid and smother flames. Foam is designed to create a blanket over the surface of flammable liquids, effectively cutting off the oxygen supply that fuels the combustion process. By smothering the flames, the foam not only prevents the fire from spreading but also helps to cool the burning area, thereby reducing the temperature and further inhibiting the fire's ability to reignite.

Other methods of firefighting involve different tactics, such as using water to absorb heat or create a barrier, but foam specifically works by both cooling and smothering, making it particularly effective for flammable liquid fires. The ability of foam to float on liquids allows it to cover and suffocate the flames, which is why it is often used in scenarios involving flammable or combustible liquids.