Oxygen tank

The vast majority of divers breathe air or nitrox stored in a diving cylinder.

Some may carry pure oxygen for accelerated decompression or as supply gas to a rebreather.

[citation needed] Oxygen is rarely held at pressures higher than 20 megapascals (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.

In some countries there are legal and insurance requirements and restrictions on the use, storage and transport of pure oxygen.

[citation needed] Oxygen tanks are normally stored in well-ventilated locations, far from potential sources of fire and concentrations of people.