Oxygen enrichment is a widespread term for any liquid or gas that contains over 21% of oxygen by volume in the air. Significant levels of oxygen can be harmful to humans in enclosed spaces.
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Why 21% Oxygen?
The median level of oxygen on Earth is around 21% oxygen by volume. The level of oxygen has remained stagnant at 21% as the amount of consumed oxygen is approximately the same as the volume of oxygen being produced over time.
There is nothing magical about 21%. It is essentially the amount of oxygen in the atmosphere in modern times. The same equilibrium is found in nitrogen (78% of air by volume) along with the trace gases such as water vapor, argon, and carbon dioxide. These numbers were different in earlier geological periods.
The earth was produced more than 4.5 billion years ago. There was essentially no free oxygen in the atmosphere at that time.
Fossil remains of oxygen-breathing mammals and human remains have been recorded over the last 150 million years and 200,000 years respectively leading experts to the conclusion that oxygen levels have increased to 21% throughout time.
While there have been small differences in the total oxygen level of the earth, throughout time humans and animals have adapted physically to breathe air that comprises approximately 21% of oxygen.
As humans and animals are used to breathing 21% of oxygen in air, anything different to 21% is dangerous to their health.
As a result, OSHA categorizes any oxygen level that is less than 19.5% as oxygen deficient and anything greater than 23.5% as oxygen-enriched air. Each one is potentially harmful.
How Much Oxygen is Too Much?
While anything greater than 23.5% oxygen is classed by OSHA as harmful, medical scientists have investigated this by exposing patients to hyperoxia, or breathing air at 100% oxygen levels for years.
Hyperbaric oxygen therapy (HBOT) utilizes 100% oxygen at an ambient pressure that is greater than atmospheric pressure. Patients are subjected to increased pressure and oxygen levels within a sealed container.
As an example, this can be employed to give supplemental oxygen to premature babies, to treat decompression sickness, and is used to treat a range of diseases under the wider term of hyperbaric oxygen therapy.
The issue with breathing air at greater oxygen levels is that within time it can harm cell membranes, causing retinal detachment, a collapse of the alveoli in the lungs, and seizures. However, studies have reported that recovery over the long term is viable once oxygen levels have decreased.
Oxygen Enrichment and Fire
While breathing air that is partially oxygen-enriched is not an issue, it does strengthen the risk of fire. Fuel, heat, and oxygen are required to start a fire. If any of these three components are significant, the risk of starting a fire is increased.
For years, firefighters have understood that when the windows of a burning building are damaged, the speedy introduction of oxygen makes a backdraft, which is the quick explosion of superheated gases in a fire with insufficient oxygen.
A further example of the risks of oxygen enrichment are welding fires. The American Welding Society (AWS) Fact Sheet, Fire and Explosion Prevention states that:
- Sparks can travel as far as 35 ft (10 m) horizontally and even more when falling. They can move through or become stuck in clothing, pipe holes, cracks, and various small openings. Sparks can be hotter than 2500 degrees F, even at 35 ft.
- Substances can be ignited by torch flames in a range of several feet around the flame.
- Any material that meets the hot workpiece can ignite, even if it is located away from the source of the flame and the actual weld.
- When high oxygen levels and high heat come together, sawdust, wood, clothing, rags, and other flammable vapors can become a possible fuel source for a fire.
Oxygen Enrichment Safety
To defend staff and workers against high levels of oxygen, GasLab provides the RAD-0012 Oxygen Enrichment Safety Alarm.
Image Credit: GasLab
This wall-mounted oxygen sensor constantly identifies levels of oxygen in enclosed areas. An alarm sounds if the levels of oxygen start to increase.
It is applied in industries that use bulk oxygen tanks such as steel manufacturing, cutting and welding, medical breathing gas, diving tanks, cryogenics, and in industries where bulk oxygen is made.
This information has been sourced, reviewed and adapted from materials provided by GasLab.
For more information on this source, please visit GasLab.