Oxygen is a colorless, odorless, tasteless elemental gas that supports life and combustion constitutes about one-fifth of the atmosphere (20.95% by volume and 23.2% by weight). At temperatures below –297.3 °F (–147.4 °C) and atmospheric pressure, it is a transparent, pale blue liquid that is slightly heavier than water. All elements except the inert gases combine directly with oxygen to form oxides. Oxygen is nonflammable, but it readily supports combustion. All materials that are flammable in air burn much more vigorously in oxygen. Some combustibles, such as oil and grease, are easily ignited and burn with nearly explosive violence in oxygen.

General precautions for safe handling of gaseous oxygen are contained in CGA G-4, Oxygen. Precautions for handling compressed gases in containers are found in CGA P-1, Safe Handling of Compressed Gases in Containers. For liquid oxygen, a thorough discussion of necessary precautions can be found in CGA P-12, Safe Handling of Cryogenic Liquids.

All easily combustible materials, especially oils and greases, must be kept from contact with oxygen. Sources of ignition should be eliminated to the extent possible. Valves should be opened slowly in order to avoid the ignition of particles carried by oxygen flowing at high velocity.

In the case of an oxygen leak or liquid oxygen spill:

• turn off all ignition sources in the general area if possible to do so safely;
• shut off the source of the leakage if possible to do so safely;
• ventilate the area;
• evacuate the area; and
• call your home oxygen supplier immediately for assistance.

Avoid contact with liquid spills. If liquid oxygen is spilled over asphalt or other surfaces, do not walk on or roll equipment over the area for at least 1/2 hour after the frost has disappeared. A violent reaction may occur simply by impact or shock.

In case of frostbite from contact with liquid oxygen, place the frostbitten part in warm water, 100 °F to 105 °F (37.8 °C to 40.6 °C). If warm water is not available, wrap the affected part gently in blankets. Let the circulation re-establish itself naturally. Encourage the victim to exercise the affected part while it is being warmed. Consult a physician.

General Information

In general, pure oxygen is a local irritant to mucous membranes, and with extended continued exposure it can be destructive to lung tissue. Thus, when oxygen treatment is used to correct hypoxia (low-oxygen concentration in the arterial blood), it should be with the minimum concentration of oxygen that will overcome the hypoxia. It should be continued only as long as necessary.

One hundred percent oxygen inhaled at atmospheric pressure can cause pulmonary irritation and edema after 24 hours of exposure. The earliest symptoms are pleuritic substernal pain and dry cough, occurring after only 6 hours. Adult respiratory distress syndrome, which involves interstitial and intra-alveolar fluid extravasation in the lung tissue, follows after 24-48 hours. Other known toxic effects include retrolental fibroplasia, which has occurred in premature infants exposed to high concentrations of oxygen at birth, retinal circulatory injury, and erythrocyte hemolysis in adults.

Inhalation of high concentrations of oxygen for a few hours has not been found to produce harmful effects except for some special classes of patients.

Special Considerations

Premature infants can suffer permanent visual impairment or blindness from inhalation of oxygen at high concentrations, and their oxygen therapy must be carefully controlled. Patients with chronic obstructive pulmonary disease retain carbon dioxide abnormally. If oxygen is administered to them, raising the oxygen concentration in the blood depresses their breathing and raises their retained carbon dioxide to a dangerous level.

High Pressure Oxygen Environments

The two systems of the body in adults most likely to be damaged by high concentrations of oxygen are the respiratory and central nervous system (CNS). Sea divers or tunnel makers are the working groups most commonly affected by high pressure oxygen environments.

When pure oxygen is inhaled at two or more atmospheres, CNS toxicity supervenes. Symptoms include nausea, vomiting, dizziness or vertigo, muscle twitching, vision changes, and loss of consciousness and generalized seizures. At three atmospheres, CNS toxicity occurs in less than 2 hours and at six atmospheres in only a few minutes. Physical exertion shortens the period before toxic symptoms and signs appear.