Wikipedia
Fog nozzle
A fog nozzle is a firefighting hose spray nozzle that breaks its stream into small droplets. By doing so, its stream achieves a greater surface area, and thus a greater rate of heat absorption, which, when compared to that of a smoothbore nozzle, speeds its transformation into the steam that smothers the fire by displacing its oxygen. Specially designed fog nozzles (with no stream adjustment) have been certified by Underwriters Laboratories (UL) for use on Class B & C hazards.