Pronounced "A-Triple-F", also called "Class B". Bubbles that act as surfactant to coat and penetrate ordinary fuels (e. g. , wood, paper) to prevent them from burning at normal temperatures; also used on "Class B" (oil/gasoline) fires to spread a non-volatile film over the surface of the fuel. Applied using eductor or Compressed air foam system (CAFS) and pumped through fire hose to a foam nozzle (or sometimes a less-effectivefog nozzle)