Its ability to cling to surfaces enables penetration, reflection of radiant heat, and suppression of oxygen. With other foams, Class A foam shares vapour suppressant and rapid flame knockdown capability. What Class A foams do not share with any other medium is performance per litre of water. Unlike aspirating nozzles, compressed air foam systems convert ninety percent of the water to foam. Systems of 40 units provide instant knockdown from 30 metres with 150 litres of water as foam.
Water conservation is a key feature.
A limited water supply cannot only be expanded, but because of the expansion, the water also becomes more effective. There are applications for both the firefighter who may have to drive to a distant water source, and the rural home owner who may have a finite water supply. Hoses filled with foam are also lighter and more manoeuvrable . The clinging, wetting, and reflecting properties of Class A foam make exposure protection perhaps its most effective application. Compressed air provides the discharge distance to reach, and the agitation to cling to walls, eaves, roofs, and trees.