Abstract: Fire retardant compositions comprising (a) ammonium sulfate; (b) a carboxyalkyl or hydroxyalkyl ether of a polygalactomannan; and optionally (c) other fire retardant chemicals from the groups consisting of monoammonium orthophosphate, diammonium orthophosphate; monoammonium pyrophosphate; diammonium pyrophosphate; triammonium pyrophosphate; tetraammonium pyrophosphate; ammonium, substituted ammonium, amide and melamine polyphosphates; ammonium-alkali metal mixed salts of ortho-, pyro- and polyphosphates; ammonium-alkaline earth metal mixed salts of ortho-, pyro- and polyphosphates; and mixtures thereof. There are disclosed both aqueous forms and concentrated non-aqueous forms of the compositions which are particularly useful for preventing, extinguishing and suppressing forest fires.