Oxygen tanks are used to store gas for:
- medical breathing at medical facilities and at home
- breathing at altitude in aviation, either in a decompression emergency, or constantly (as in unpressurized aircraft)
- oxygen first aid kits
- oxygen therapy
- gas blending, for creating diving breathing mixes such as nitrox, trimix and heliox
- open-circuit scuba sets – mainly used for accelerated decompression in technical diving
- some types of diving rebreather: oxygen rebreathers and fully closed circuit rebreathers
- use in climbing, “Bottled oxygen” refers to oxygen tanks for mountaineering
- industrial processes, including the manufacture of steel and monel
- oxyacetylene welding equipment, glass lampworking torches, and some gas cutting torches
- use as liquid rocket propellants for rocket engines
- athletes, specifically on American football sidelines, to expedite recovery after exertion.
Breathing oxygen is delivered from the storage tank to users by use of the following methods: oxygen mask, nasal cannula, full face diving mask, diving helmet, demand valve, oxygen rebreather, built in breathing system (BIBS), oxygen tent, and hyperbaric oxygen chamber.
Contrary to popular belief scuba divers very rarely carry oxygen tanks. The vast majority of divers breathe air or nitrox stored in a diving cylinder. A small minority breathe trimix, heliox or other exotic gases. Some of these may carry pure oxygen for accelerated decompression or as a component of a rebreather. Some shallow divers, particularly naval divers, use oxygen rebreathers or have done so historically.
Oxygen is rarely held at pressures higher than 200 bars (3,000 psi), due to the risks of fire triggered by high temperatures caused by adiabatic heating when the gas changes pressure when moving from one vessel to another. Medical use liquid oxygen airgas tanks are typically 350 psi (24 bar).
All equipment coming into contact with high pressure oxygen must be “oxygen clean” and “oxygen compatible”, to reduce the risk of fire. “Oxygen clean” means the removal of any substance that could act as a source of ignition. “Oxygen compatible” means that internal components must not burn readily or degrade easily in a high pressure oxygen environment.
In some countries there are legal and insurance requirements and restrictions on the use, storage and transport of pure oxygen. Oxygen tanks are normally stored in well-ventilated locations, far from potential sources of fire and concentrations of people.