Fire Safety Science Digital Archive

The effectiveness of high expansion foam with air was first examined by the Safety in Mines Research Establishment at Buxton and later, a portable air-foam generator was developed in America. Some early tests of high expansion foam made with the J.F.R.O. Inert Gas and Foam Generator are described elsewhere. The extinguishing properties of high expansion foam depends mainly on the quantity of liquid, mainly water, transported to the fire, and the restriction of the supply of oxygen at the combustion zone. The amount of water conveyed to a fire by high expansion foam can be maintained at a high level by the use of a foaming agent giving the requisite properties of low rate of break-down and drainage. The reduction in the oxygen content of the atmosphere surrounding the combustion zone depends upon the reduction in oxygen content produced by the evaporation of the water present in the foam, and also upon the initial oxygen content of the gas in the bubbles. The oxygen content of the gas filling the bubbles is lower than atmospheric concentration when the jet-engine exhaust gases are used for generation. This note describes and presents the results of a series of experiments to investigate these factors, using high expansion foams made with air, and with gas from the J.F.R.O. Inert Gas Generator.