How is pressure applied in a foam extinguisher?

In a foam extinguisher, pressure is applied by compressed air. This method is integral to the functioning of the extinguisher, as it allows for the effective expulsion of the foam solution aimed at suppressing fires. The compressed air forces the liquid foam mixture out of the nozzle, creating a spray or blanket of foam that can smother flames, cool hot surfaces, and prevent the release of flammable vapors. This mechanism not only facilitates the distribution of the foam but also ensures that it adheres to the surfaces being protected, enhancing its effectiveness in fire suppression.

Using compressed air for pressure generation is common in various fire suppression systems, as air can easily be pressurized and stored within the extinguisher, ready for immediate use in emergencies. The other methods listed, whilst relevant to different contexts or types of equipment, do not describe the primary mechanism for a foam extinguisher.