This invention relates to an improved portable system for the delivery of a breathable, fire extinguishing gas mixture to a fire zone. The gas mixture comprises a normally gaseous inert material, such as nitrogen, helium or argon; an oxygen containing gas; and carbon dioxide. The system includes a means for storing or generating the inert material, means for storing the carbon dioxide, means for generating or introducing the oxygen containing gas, and means for mixing the components. The system also includes means for heating, vaporizing and controlling the temperature and proportions of the components.