Abstract: A stable foam concentrate of low viscosity is diluted with water and foamed to form a foam suitable for application to fires and spills of polar liquids or water-immiscible organic materials. The concentrate is an essentially aqueous solution containing 4% to 6% citrus pectin, 3% to 9% alkylbetaine surfactant, 9% to 20% sodium alkyl sulfate surfactant, 4% to 12% alkoamphoglycinate or alkoamphopropionate surfactant, the total amount of surfactant being at least 30%. The concentration may also contain 1% to 4% of a fluorine substituted thioether.