Aircraft Hangar High Expansion Foam System Test

When the High Expansion Foam is discharged into a fire compartment, three extinguishing mechanisms simultaneously occur:
1. The large mass of the discharging foam fills all voids and seals the area involved in the fire and prevents fresh air from reaching the base of the flames. The foam mass maintains an oxygen deficient area until the fire is extinguished.
2. The steam generated is a result of the radiant heat from the fire evaporating the water in the foam blanket. This conversion to steam absorbs large quantities of heat and the resulting steam-air mixture is well below the oxygen level that is required to support continued combustion.
3. The cooling effect of the Hi-Ex foam occurs as the bubbles break and release water onto any hot surfaces. The surface tension of the draining water is lowered and the cooling and wetting effect of the draining water penetrates any Class "A" type materials more rapidly than water. This cools the burning material to below its ignition
temperature.