Liquid Oxygen Systems

Liquid oxygen systems are frequently prescribed for individuals who are mobile and active outside their homes. In its liquid state, oxygen takes up less space and can be stored at much lower pressures than when in its gaseous state. This means more oxygen can be carried in a portable liquid unit, and the portable container is much lighter in weight than an oxygen gas cylinder.

Liquid oxygen systems consist of a stationary unit or reservoir which stores a large volume of liquid oxygen and a portable unit which can be refilled from the reservoir. When you are at home, you will probably use the stationary unit as your source of oxygen. But, for exercise or other activities outside your home, or within the home out of reach of your stationary source, you can fill the portable unit and be free to go wherever you choose.

To remain in a liquid form, oxygen must be stored at approximately minus 300 degrees F. For this reason the reservoir and the portable unit are actually large thermos containers. When you turn ON the oxygen, the liquid warms as it leaves the container, changes to gas, and is supplied at room temperature for you to breathe.

Medicare Information and Qualifications:

The patient must qualify for oxygen and then the physician will determine the type of equipment the patient will need.

General Coverage Guidelines

Home oxygen is covered and paid by Medicare if the following conditions are met:

  1. The patient has a severe lung disease or hypoxia-related symptoms that the physician has determined may improve with oxygen therapy.
  2. The patient’s blood gas study meets qualifying oxygen levels.
  3. The treating physician tried or considered alternative treatment measures and determined them to be ineffective.

Not Medically Necessary

  • For these situations, get an ABN to cover yourself, even if filing non-assigned.
  • Terminal illnesses that do not affect the respiratory system.
  • Angina pectoris in absence of hypoxemia.
  • Dyspnea without cor pumonale (or evidence of hypoxemia).
  • Severe peripheral vascular disease.

Summary: Certificates of Medical Necessity

To communicate qualifying medical necessity information to Medicare, claims must be billed with a Certificate of Medical Necessity. This is accomplished using the OMB approved form (CMS-484).

The items listed below are often sold, prescribed or needed in addition to the equipment above.

  • Carrying bag for portable system
  • Cart

Disclaimer: This is a sampling of information. Please refer to the CMS website ( and consult your own experts for additional information.