AFFF foam deals with Class A fires, however, can also snuff out class B/ combustible liquid fires. When sprayed onto a fire, AFFF foam snuffs out and smothers the flames, then seals in any hazardous vapours under the surface of the foam. Foam likewise penetrates permeable materials and cools the fire as the water in the foam vaporises. As the foam extinguisher is conductive, they must not be used near or on active electrical devices. Their blue colour coded band can distinguish foam fire extinguishers.
For more details check out our article All About Foam Fire Extinguishers