Oxygen can be separated by a number of methods, including chemical reaction and fractional distillation, and then either used immediately or stored for future use.
The main types of sources for oxygen therapy are:
Liquid storage – Liquid oxygen is stored in chilled tanks until required, and then allowed to boil (at a temperature of 90.188 K (−182.96 °C)) to release oxygen as a gas.
This is widely used at hospitals due to their high usage requirements, but can also be used in other settings.
See Vacuum Insulated Evaporator for more information on this method of storage.

Compressed gas storage – The oxygen gas is compressed in a gas cylinder, which provides a convenient storage, without the requirement for refrigeration found with liquid storage.
Large oxygen cylinders hold 6,500 litres (230 cu ft) and can last about two days at a flow rate of 2 litres per minute.
A small portable M6 (B) cylinder holds 164 or 170 litres (5.8 or 6.0 cu ft) and weighs about 1.3 to 1.6 kilograms (2.9 to 3.5 lb).
These tanks can last 4–6 hours when used with a conserving regulator, which senses the person's breathing rate and sends pulses of oxygen.
Conserving regulators may not be usable by people who breathe through their mouths.

Instant usage – The use of an electrically powered oxygen concentrator  or a chemical reaction based unit can create sufficient oxygen for a person to use immediately, and these units (especially the electrically powered versions) are in widespread usage for home oxygen therapy and portable personal oxygen, with the advantage of being continuous supply without the need for additional deliveries of bulky cylinders.
Oxygen can be separated by a number of methods, including chemical reaction and fractional distillation, and then either used immediately or stored for future use. The main types of sources for oxygen therapy are:
Liquid storage – Liquid oxygen is stored in chilled tanks until required, and then allowed to boil (at a temperature of 90.188 K (−182.96 °C)) to release oxygen as a gas. This is widely used at hospitals due to their high usage requirements, but can also be used in other settings. See Vacuum Insulated Evaporator for more information on this method of storage.
Compressed gas storage – The oxygen gas is compressed in a gas cylinder, which provides a convenient storage, without the requirement for refrigeration found with liquid storage. Large oxygen cylinders hold 6,500 litres (230 cu ft) and can last about two days at a flow rate of 2 litres per minute. A small portable M6 (B) cylinder holds 164 or 170 litres (5.8 or 6.0 cu ft) and weighs about 1.3 to 1.6 kilograms (2.9 to 3.5 lb). These tanks can last 4–6 hours when used with a conserving regulator, which senses the person's breathing rate and sends pulses of oxygen. Conserving regulators may not be usable by people who breathe through their mouths.
Instant usage – The use of an electrically powered oxygen concentrator  or a chemical reaction based unit can create sufficient oxygen for a person to use immediately, and these units (especially the electrically powered versions) are in widespread usage for home oxygen therapy and portable personal oxygen, with the advantage of being continuous supply without the need for additional deliveries of bulky cylinders.
Oxygen therapy