Abstract: A foam generating device includes a source of compressed gas and a source of liquid adapted to produce a foam. A gas operated pump such as a diaphragm pump is provides which has a gas inlet communicating with the compressed gas source to drive the pump, a gas exhaust, a liquid inlet and liquid discharge to discharge said liquid from the pump. An injector disposed at the discharge side of the pump and is in communication with the gas outlet of the pump to inject exhaust gas into the liquid discharged by the pump to aerate the liquid and produce a foam. The device may be portable, vehicle mounted or stationary. The liquid may be water with an injector to inject a foaming agent into the water.