A chemical oxygen generator is a device that releases oxygen via a chemical reaction. The oxygen source is usually an inorganic superoxide,[1] chlorate, or perchlorate. Ozonides are a promising group of oxygen sources, as well. The generators are usually ignited by a firing pin, and the chemical reaction is usually exothermic, making the generator a potential fire hazard. Potassium superoxide was used as an oxygen source on early crewed missions of the Soviet space program, in submarines for use in emergency situations, for firefighters, and for mine rescue.