Abstract: An oxygen supply apparatus, particularly for use by a coal miner, has a plurality of housings mounted on a belt, which is worn by the miner, with each housing having a cartridge of oxygen generating material therein and removable from the bottom thereof for replacement. Each housing has a cover with a resiliently biased shaft supported thereby for relative movement to activate the oxygen generating material in the cartridge. The shaft functions as a timer activator so that the timer is set when the shaft is activated. The timer produces an alarm signal just prior to the expiration of time for depletion of oxygen from the cartridge within the housing. Each of the covers has a chamber receiving the oxygen from the cartridge and supplying it through tubing to oxygen receiving means worn by the miner such as a mask, for example.