What Is Liquid Oxygen?

Liquid oxygen is oxygen that’s cooled to -183° C (-297°F) at which point it becomes a pale blue liquid.[1] It is one of the physical forms of the element and serves as an efficient means of supplying home oxygen to a variety of patients.

Liquid Oxygen Supply Systems

The liquid oxygen supply system usually consists of a bulk storage unit or reservoir that’s housed in a permanent place in the home and a refillable, portable unit that you can carry around. The reservoir and portable units have a design similar to that of a thermos bottle, consisting of a container inside a container separated by a vacuum. To remain in liquid form, the oxygen must be stored at very cold temperatures inside the thermos-like container. When you’re ready to use the oxygen and you turn it ON, the liquid warms as it leaves the container, changes to gas, and is supplied at room temperature for you to breathe. Depending upon the manufacturer, there are a wide variety of styles and sizes of liquid oxygen systems, each operating under the same principle.[2]

Understanding the Bulk Stationary Storage Unit

Oxygen is often stored as a liquid – although it’s used primarily as a gas – because it’s less bulky and less expensive than storing the equivalent capacity of high-pressure gas. One liter of liquid oxygen is equivalent to approximately 860 liters of gaseous oxygen. A typical bulk storage unit is filled with approximately 40 liters of liquid oxygen. This may be more than 11 days at a flow rate of 2 liters per minute.[3] When you’re at home, you can use the stationary unit as your primary oxygen source. Depending upon your flow rate, your oxygen supply company will routinely refill the stationary storage unit every 1 to 2 weeks.

Understanding the Portable Container

The portable carrying container can be refilled from the large storage unit whenever necessary. When full, the portable unit typically weighs between 6 and 11 pounds and provides approximately 1,025 liters of gaseous oxygen. When you’re at home and out of reach of your stationary unit, you exercise or perform activities outside the home, you can fill the portable system and be free to go wherever you choose.  Because oxygen in its liquid state takes up less space and can be stored at much lower pressures than when in its gaseous state, the portable unit carries more oxygen and is much lighter than a standard oxygen gas cylinder.[3]

Is a Liquid Oxygen Supply System for Me?

Choosing an oxygen supply system is one of the most important decisions you will ever make. If you’re having trouble deciding whether a liquid oxygen system is right for you, it’s a good idea to compare the advantages and disadvantages of different systems.

One of the biggest advantages of using liquid oxygen is that it consumes no electricity. This may be ideal for people on fixed incomes who are unable to afford the higher electricity bills that come with using an oxygen concentrator. Portable liquid oxygen tanks are also lighter and take up less space than compressed gas cylinders making them easier to transport. But oxygen in its liquid form can be more expensive than compressed gas. It can’t be stored for long periods of time because it tends to evaporate. Because the main system needs to be refilled on a regular basis by a service technician, you’re subject to scheduling deliveries, which may be inconvenient. Lastly, refilling the portable tank is said to require dexterity and strength which some folks find difficult.[3]

The Bottom Line

The right oxygen supply system is one that meets your needs and suits your lifestyle. Before you make that choice, talk to your primary health care provider about each system’s pros and cons.


  1. Properties of Oxygen; Oxygen | Liberty Industrial Gases and Welding Supply, Inc. (libertygases.com)
  2. Getting Started with Liquid Oxygen American Lung Association
  3. Hardavella G, Karampinis I, Frille A, Sreter K, Rousalova I. Oxygen devices and delivery systems. Breathe (Sheff). 2019 Sep;15(3):e108-e116. doi: 10.1183/20734735.0204-2019. PMID: 31777573; PMCID: PMC6876135. Oxygen devices and delivery systems – PMC (nih.gov)
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