Oxygen basics for pilots
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Did you know that not all oxygen is the same?
Supplemental oxygen is used to prevent hypoxia during flying.
Supplemental oxygen is used to prevent hypoxia during flying. Reduced atmospheric pressure means less oxygen in your lungs and less oxygen in your tissue. Symptoms of hypoxia are cyanosis (a blue tint to the tissue around the tips of your extremities and lips), tingling or numbness in the extremities, and a feeling of euphoria. As hypoxia progresses you become sleepy
If not corrected it will lead to unconsciousness and death.
FAR 91.211 (supplemental oxygen) provides oxygen use requirements including the altitudes at which pilots must use supplemental oxygen and provide oxygen for passengers. Oxygen is also recommended when flying at night at above 5000 feet (see this post on the oxygen use requirements at Sportys.com/blog.)
Pilots can monitor their oxygen saturation, or SPO2, which is the percentage of oxygen their blood cells are carrying, via a pulse oximeter. Normal oxygen saturation is 96% or higher when breathing the air on the ground. This saturation number will decrease as altitude increases due to the atmosphere becoming less dense the higher we fly.
Our atmosphere is made up of 21% oxygen and 78% nitrogen; the remaining 1% is small amounts of different gases.
The most common way to deliver oxygen is from an installed system or a portable system. Both systems consist of a tank, a regulator (controls the flow), and either a mask or nasal cannula that the pilot and passengers wear. Oxygen cannulas are not approved for use above 18,000 feet. Above this altitude, you must wear a mask. Some systems also include a directional flow indicator to indicate that oxygen is moving from the tank to the mask or cannula.
The most common way to deliver oxygen is from an installed system or a portable system.
All oxygen is not the same.
There are three grades of oxygen: medical oxygen, aviator oxygen, and industrial oxygen.
Medical and aviator oxygen is 99.5% pure, and industrial, or welders oxygen, is 99.2% pure. The biggest difference between medical and aviator oxygen is the moisture content. Medical oxygen can contain 67 ppm of moisture. Industrial oxygen can contain 50 ppm of moisture. Aviation oxygen can contain 7 ppm of moisture—this is very dry oxygen as moisture in an oxygen system can freeze at altitude and prevent the system from working correctly. Another difference is that medical oxygen typically requires a prescription from a physician.
The last grade is industrial oxygen which is used for welding purposes. This grade of oxygen typically has a high percentage of moisture and is not filtered for very small particulates and is not as pure.
You should always ensure that you are using aviator oxygen when flying. Use of other grades can lead to hypoxia.
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I’d be interested in seeing a citation regarding your comments about the different types of oxygen.
Recommend you check sources. Although the requirements are as stated, the guys who sell gas products here tell me that they have only one grade of O2 due to economies of having a single product that meets all needs. Thus all their O2 is medical grade with low moisture. Certainly not a gas product employee or professional, but that’s what they said. It apparently changed when technology developed which made it easier to get the extra .3%; about the same time they started putting OBOGS in planes.
You might find this brief article to be of interest:
https://www.aopa.org/news-and-media/all-news/2023/december/pilot/oxygen-is-oxygen
According to an AOPA article, oxygen is oxygen. They have all been the same for some time.
https://www.aopa.org/news-and-media/all-news/2023/december/pilot/oxygen-is-oxygen
Jeff, you are absolutely right. All oxygen is the same.
This info is outdated. The article cites info that applied to oxygen produced by procedures in the 1950s, but not today. Current O2 is all cryogenically produced, and is exactly the same. It meets specs for all three customers, medical, industrial, and ABS. Also, there is no operational requirement to use a mask above 18,000′. That is a production spec found in FAR 23.1447(c) and is not an operational spec. (nor are most GA airplanes flying today subject to FAR 23, they were manufactured well before this reg was created). 91.211 is the operational spec for O2 use. If your method of providing oxygen supplies sufficient blood O2 saturation, that’s the key.
I suggest you read a rather old, but well written article by John Deakin at https://www.avweb.com/features/pelicans-perch-13getting-high-on-welders-oxygen/.
I am sorry but I believe the last sentence is simply misleading. Using medical oxygen in a portable system that is inside a warm cabin will not cause icing unless the flow is measured in tons per minute.
And as most said – nowadays even industrial oxygen is made the same way as the aviation oxygen. I believe however that they test medical oxygen before filling a tank.
Disappointed in the quality of this article.