Oxygen (O2) is a colorless, odorless gas essential for most life on Earth, enabling aerobic respiration to convert nutrients into energy. While the atmosphere provides a constant supply, specialized methods exist for accessing and concentrating oxygen. These methods are used for applications ranging from therapeutic use to industrial processes.
The Earth’s Natural Oxygen Supply
The primary natural source of oxygen is photosynthesis, a biological process performed by plants on land and microscopic organisms like cyanobacteria and phytoplankton in the oceans. During photosynthesis, these organisms use sunlight, water, and carbon dioxide to create energy, releasing oxygen as a byproduct.
The atmospheric air we inhale is a mixture of gases, not pure oxygen. Oxygen makes up approximately 20.95% of the atmosphere by volume, while the majority, about 78.08%, is composed of nitrogen. This concentration is maintained through a global cycle where photosynthetic organisms produce oxygen and aerobic life consumes it.
Medical Oxygen Sources and Delivery
For therapeutic purposes, oxygen is a regulated medical treatment requiring a prescription from a healthcare provider. Medical-grade oxygen must meet strict purity standards to ensure patient safety and is sourced from specialized medical gas suppliers. These suppliers ensure the product is highly controlled and free from contaminants like carbon monoxide or excessive moisture.
Oxygen Concentrators
One common source is the oxygen concentrator, a medical device that draws in ambient air and filters it electronically. It uses Pressure Swing Adsorption (PSA) to physically separate nitrogen molecules from the air using materials like zeolite. The resulting output is concentrated oxygen, typically delivered at a purity of \(93\%\pm3\%\).
Stored Oxygen Systems
Other delivery methods rely on a finite supply of stored oxygen. Pressurized gas tanks, or cylinders, contain highly compressed gas and are often used for portability or as a backup supply. Liquid oxygen systems store the gas cryogenically, allowing a large volume of oxygen to be contained in a smaller canister. Liquid systems provide oxygen that is nearly 100% pure and are often reserved for patients with the highest needs.
Commercial and Recreational Oxygen Uses
Oxygen is widely utilized in non-medical and industrial settings, where purity requirements and delivery systems differ significantly from medical use. Industrial-grade oxygen is used for applications such as metal fabrication, including welding and cutting. This grade is not regulated for human consumption and may contain trace contaminants, but it is cost-effective and usually supplied as a compressed gas.
Specialized Breathing Applications
For specialized breathing applications, such as scuba diving and aviation, oxygen requires a higher purity than standard industrial gas. Aviation oxygen is filtered to a minimum purity of 99.5% and has very low moisture content. This low moisture prevents delivery systems from freezing at high altitudes and is also used by gas blenders to create breathing mixes for technical scuba diving.
A less regulated category involves novelty and recreational uses, such as canned oxygen and oxygen bars. These products are not considered therapeutic and do not require a prescription. Oxygen bars typically use concentrator technology to provide air enriched with 88% to 90% oxygen for users to breathe for short periods.