A suspension in the atmosphere of water divided into coarse drops by delivery through a special nozzle for use in fire fighting. When water fog hits the fire and hot surfaces, it vaporises and expands 17,000 times. Once expanded the water vapour gives off the oxygen to quell the fire in addition to the cooling effect of the mist. See also Hi-Fog system.
Water fog is supplied through a system of high pressure water lines and fog nozzles. A ring of nozzles around the inside of the tank opening effectively suppresses a cargo tank hatch fire.