Oxygen tanks are used to store gas for:

medical breathing at medical facilities and at homebreathing at altitude in aviation, either in a decompression emergency, or constantly (as in unpressurized aircraft)oxygen first aid kitsoxygen therapygas blending, for creating diving breathing mixes such as nitrox, trimix and helioxopen-circuit scuba sets - mainly used for accelerated decompression in technical divingsome types of diving rebreather: oxygen rebreathers and fully closed circuit rebreathersuse in climbing, Bottled oxygen refers to oxygen tanks for mountaineeringindustrial processes, including the manufacture of steel and moneloxyacetylene welding equipment, glass lampworking torches, and some gas cutting torchesuse as liquid rocket propellants for rocket enginesathletes, specifically on American football sidelines, to expedite recovery after exertion.[1]