Pure oxygen has a wide range of uses, from keeping critically ill patients alive to powering rockets into space. In medicine, it treats conditions like carbon monoxide poisoning and decompression sickness. In industry, it drives chemical reactions and serves as rocket fuel oxidizer. Here’s a closer look at where and why 100% oxygen is used.
Emergency and Critical Care Medicine
The most common use of pure oxygen is in medical emergencies. When your blood oxygen levels drop dangerously low, a condition called hypoxemia, breathing concentrated oxygen can prevent organ damage and death. This happens in a range of serious situations: severe pneumonia, major trauma, cardiac arrest, and carbon monoxide exposure.
During CPR, the highest possible oxygen concentration is delivered to keep the brain and heart supplied while the team works to restore a heartbeat. Once circulation returns, the dose is typically dialed back to maintain blood oxygen saturation between 94% and 98%. Delivering a full 100% concentration requires either a mechanical ventilator or a tight-fitting face mask, since standard nasal tubes mix in room air and dilute the oxygen.
Carbon monoxide poisoning is one of the clearest cases for pure oxygen. Carbon monoxide binds to red blood cells far more aggressively than oxygen does, essentially blocking your blood from carrying oxygen to your tissues. Flooding the lungs with 100% oxygen forces the carbon monoxide off those blood cells much faster than breathing normal air would.
Hyperbaric Oxygen Therapy
Hyperbaric oxygen therapy (HBOT) takes things a step further. You breathe pure oxygen inside a pressurized chamber, which dissolves far more oxygen into your blood plasma than normal breathing ever could. This supercharges oxygen delivery to damaged or oxygen-starved tissues.
There are currently 14 approved medical uses for HBOT. They fall into three broad categories: accelerating wound healing, fighting infections, and treating medical emergencies. The full list includes:
- Emergency conditions: air or gas embolism, decompression sickness, carbon monoxide poisoning (including cases complicated by cyanide poisoning), and severe anemia
- Wound and tissue repair: crush injuries, compromised skin grafts, delayed radiation injury to soft tissue or bone, stubborn non-healing wounds, and acute thermal burns
- Infections: gas gangrene, necrotizing soft tissue infections (sometimes called flesh-eating bacteria), refractory bone infections, and intracranial abscess
- Other: central retinal artery occlusion (a type of eye stroke) and sudden sensorineural hearing loss with no known cause
For divers with decompression sickness, pure oxygen is especially critical. When a diver ascends too quickly, dissolved nitrogen forms bubbles in the blood and tissues. Breathing 100% oxygen helps clear those nitrogen pockets, even before the diver reaches a hyperbaric chamber. Current guidelines call for 100% oxygen to be given immediately to any diver suspected of decompression sickness, regardless of what their oxygen saturation reads.
Rocket Propulsion
Outside of medicine, one of the most dramatic uses of pure oxygen is as a rocket propellant. Liquid oxygen (often abbreviated LOX) serves as the oxidizer in liquid-fueled rocket engines. In a combustion chamber, the oxidizer and a fuel like liquid hydrogen or kerosene are pumped together, mixed, and ignited. The resulting exhaust gases reach extreme temperatures and pressures, then accelerate through a nozzle to produce thrust.
The key advantage of carrying liquid oxygen on board is that rockets can operate in the vacuum of space, where there’s no atmospheric oxygen to support combustion. Without an onboard oxidizer, chemical rockets simply wouldn’t work beyond Earth’s atmosphere. NASA and commercial launch providers rely on LOX as a standard component of their propulsion systems.
Industrial Chemical Production
Many industrial chemical processes depend on controlled oxidation reactions, and pure oxygen gives manufacturers precise control over those reactions. One major example is the production of ethylene oxide, a chemical used to make antifreeze, plastics, detergents, and to sterilize medical equipment. In the production process, oxygen concentration directly affects the quality and yield of the final product. Too much oxygen and the ethylene gets fully oxidized into useless carbon dioxide and water instead of the desired ethylene oxide.
Steel manufacturing is another major consumer. Blasting pure oxygen into molten iron burns off excess carbon and impurities far more efficiently than blowing regular air. Welding and metal cutting also use pure oxygen to achieve the higher flame temperatures needed to work with thick or high-melting-point metals.
Risks of Pure Oxygen
Pure oxygen is not harmless, and its dangers come in two main forms: fire hazard and oxygen toxicity inside the body.
Oxygen itself doesn’t burn, but it makes everything around it burn faster and hotter. Normal air contains about 21% oxygen. At just 23%, clothing and bed linens can ignite more easily. At 24%, workers need fire-resistant protective equipment. At 25%, hair and clothing burn rapidly and aggressively. The minimum temperature and energy needed to start a fire both drop as oxygen concentration rises, which is why hospitals take strict precautions around patients receiving supplemental oxygen.
Inside the body, breathing pure oxygen at high pressure or for extended periods causes two types of toxicity. Pulmonary toxicity affects the lungs, gradually reducing their capacity. The damage depends on both the pressure of oxygen breathed and the duration of exposure. The U.S. Navy sets exposure limits designed to keep lung capacity loss below 2%, with a maximum acceptable loss of 10%. Central nervous system toxicity is the more immediately dangerous form, potentially causing seizures. It generally requires oxygen pressures above about 1.3 times normal atmospheric pressure, which is why it’s primarily a concern for divers and hyperbaric patients rather than people on hospital oxygen masks.
Recreational Oxygen Bars
Oxygen bars, where customers pay to breathe flavored oxygen through a nasal tube for 15 to 20 minutes, have been marketed as boosting energy, reducing stress, and promoting relaxation. The evidence doesn’t support those claims. A randomized study that measured energy, relaxation, and stress levels in oxygen bar users found no significant differences between people breathing supplemental oxygen and those who weren’t. For healthy individuals with normal lung function, the body already saturates blood with oxygen at close to 100% efficiency, so breathing extra oxygen provides no measurable benefit.