Foam fire extinguishers have come a long way in 30 years. The original foam was thick, gloopy and smelled appalling, due to its high animal protein content. Modern Aqueous Film Forming Foam (AFFF) fire extinguishers are another breed altogether, one of the best all-round units available. Foam extinguishers are red with a cream panel above the operating instructions. Foam is extremely effective on Class A fires, involving paper, wood, etc, so they are a good choice for a general office or location fire extinguisher. They are particularly great on man-made furnishings, where the fibres in the fabrics might otherwise liquify in the heat of the fire. When used on flammable liquid fires (Class B), the foam forms a film that prevents re-ignition of the flammable liquids by sealing the liquids away from oxygen in the air.