Information on the use of supplemental oxygen in general aviation aircraft.

by: Jerry Nelson(Edited and updated by Brad D LeHuquet of Precise Flight.)

The following information is presented to give the reader an informal overview on the use of oxygen in general aviation aircraft at all altitudes. The remaining atmosphere consists of 78% nitrogen and 1% traces of other gases. Oxygen under normal conditions is an odorless, colorless, tasteless, non-combustible gas. It is the most important single element on earth.

At each breath we fill our lungs with air. Millions of tiny air sacs (known as "alveoli") in our lungs inflate like tiny balloons. In the minutely thin walls enclosing each sac are microscopic capillaries through which blood is constantly transported, from the lungs to every cell in the body. The blood carries the oxygen extracted from the air in the lungs to every part of the body. Because the body has no way to store oxygen over a long period of time, it leads a breath-to-breath existence.

The human body must have oxygen to convert fuel (the carbohydrates, fats, and proteins in our diet) into heat, energy, and life. The conversion of body fuels into life is similar to the process of combustion fuel. Oxygen is consumed, while heat and energy is generated. This process is known as "metabolism".

The rate of metabolism, which determines the need for and consumption of oxygen, depends on the degree of physical activity or mental stress of the individual. Not all people require the same amount of oxygen. A man walking at a brisk pace will consume about four times as much oxygen as he will while sitting quietly. Under severe exertion or stress, he could possibly be consuming eight times as much oxygen as resting.

There are three kinds of oxygen that are merchandised or sold to users; Aviation, Medical, and Welding. There is an ongoing controversy whether or not there is any difference between the different types. Oxygen gas is produced from the boiling off of liquid oxygen. It would appear that the oxygen is, therefore, the same. Where we obtain oxygen, all the different types of oxygen are supplied from the same manifold system.

Then someone says that medical oxygen has more moisture in it. That is partly true. The oxygen going to a hospital bed is plain oxygen that comes from liquid oxygen. At the bed location, there is a unit on the wall that adds moisture. At this moment we now have medical oxygen. If the oxygen is in a pressure vessel or in a manifold system (like inside a hospital) then it is regular oxygen. The cost of medical or welding oxygen is normally much less than the oxygen you get at an airport.

Also of interest, the suppliers of welding oxygen have told us, the purity level required for welding and cutting purposes is more critical than for breathing.

The bottom line about the different types of oxygen is in the insurance liability of the oxygen supplier. The gas is the same but the insurance liability is different. The welding gas company may or may not supply you with oxygen for your aircraft. Likewise the medical oxygen supplier may or may not supply you with oxygen for your aircraft. Some of our customers have told us that they can only get medical oxygen for aircraft use if they have a prescription from their family doctor.

We ask you to determine if the welding or medical oxygen is suitable for your use. We do not and cannot make any recommendation on the use of oxygen other than aviation oxygen.