The effects of ammonium salts of sulfaminic acids, containing aliphatic and arylaliphatic hydrocarbon chains, respectively, in a combination with inorganic fire retardants and fillers, on the properties of ethylene-propylene copolymer compositions (EPCC) for cable insulation were studied. The additive action of the organic fire retardants and antimony oxide in a weight ratio of 3:1 was proved. EPCC indicated a limited oxygen index (LOI) of 37-39% and a diminished smoke release and belonged to UL class zero. The thermal destruction of the system consisting of a copolymer blend and fire retardant, as well as the individual organic and inorganic fire retardants, was studied using dynamic thermal analyses (DTA, TG, DTG). The combination of fire retardants caused a decrease of both the heat release and weight loss over the EPCC surface.