Foam extinguishes a fire by separating, cooling, and what else?

Foam extinguishes a fire primarily through three mechanisms: separating, cooling, and suppressing. The separation occurs as foam forms a barrier between the fuel and the fire, preventing the oxygen from reaching the fuel and thus interrupting the combustion process. Cooling is achieved as the foam also lowers the temperature of both the fuel and the surrounding area.

Suppressing refers to the ability of foam to reduce the release of flammable vapors from the surface of the burning fuel. By covering the fuel with foam, it limits the amount of vapor that can escape into the air, thereby reducing the possibility of re-ignition and making it harder for the fire to sustain itself. This is crucial at airports where flammable materials are present and rapid response to fires is needed.

The other options do not represent mechanisms by which foam effectively extinguishes fires. Thus, suppressing stands out as the correct answer in this context.