Thermally stable gas generant compositions incorporate a combination of one or more primary nonazide high-nitrogen fuels selected from a group including tetrazoles, bitetrazoles, and triazoles, and salts thereof; and one or more secondary nonazide high nitrogen fuels selected from azodicarbonamide and hydrazodicarbonamide. The primary and secondary fuels are combined with phase-stabilized ammonium nitrate that when combusted, results in a greater yield of gaseous products per mass unit of gas generant, a reduced yield of solid combustion products, lower combustion temperatures, and acceptable burn rates, thermal stability, and ballistic properties. These compositions are especially suitable for inflating air bags in passenger-restraint devices.