What does a foam fire extinguisher do to stop a fire?

The correct answer highlights the primary mechanism by which foam fire extinguishers operate to control and extinguish fires. Foam fire extinguishers create a thick, stable foam that blankets the surface of the burning material. This foam serves two critical functions: it helps to smother the fire and effectively cuts off the oxygen supply that the fire needs to continue burning.

By displacing the oxygen above the flames, the foam helps to cool the fire while simultaneously preventing re-ignition, creating a barrier between the fuel and the heat. This is particularly effective for fires involving flammable liquids or solids, as the foam can also help to suppress the release of flammable vapors.

Understanding this function of a foam fire extinguisher is crucial for effective fire safety management and response, especially in environments where flammable liquids are present.