Five Letters Re: Welding Oxygen Versus Medical Oxygen

Just a quick note, never ever use oxygen under pressure near oil! Never use oil on the thread’s or fittings! The high pressure will cause the oil to detonate,similar to a diesel ignition! If you must,and probably should never need to, use a teflon tape seal!And if you have an acetylene bottle, let it stand for 24 hours as it may have been laid on it’s side before using it, separating the acetone from the gas. – Dean


The letter in response to welding oxygen versus medical oxygen was interesting. Unfortunately [that readers} was wrong on one point. Oil is never used around oxygen, period. Quoting from a Compressed Gas Association safety alert “Liquid oxygen containers must be properly cleaned for oxygen service and must be kept clean and free of grease, oil, or other hydrocarbon materials, which can combine with oxygen with explosive violence.”

The other danger is that the manufacturer does not know what the end use of the gas will be. If they allow any impurities in it, they could be liable for contaminating an end product of causing a substandard weld. I can assure you that virtually all oxygen is safe for human use. – Docliberty


If you go to a local oxygen supplier and ask, (and they are being honest) they will tell you that they fill the welding oxygen, the aviators oxygen and the medical grade oxygen tanks from the exact same bulk tank, which is to say, they are all medical grade.
The previous e-mail is correct in that it is important to know that if you are using a compressor for breathable air, it should be medical grade, preferably an oil-less compressor.
His/her reasoning is correct but in the oxygen industry, no one I know makes their own oxygen with compressors on premises any more. Rather, they buy in bulk from dealers (You can make oxygen yourself with an oxygen concentrator but then you are back to needing electricity.) and the dealers only make one grade: medical grade.

The difference is not in the quality of the oxygen but the chain of custody of the tanks. If you bring an oxygen tank in to get refilled, they will give you another refilled oxygen tank of the same category (i.e. welding, aviators or medical) that you gave them but not likely the exact one you brought in. Here’s the issue: If a welding tank is used, you don’t know where it’s been and if it has been left open, contaminants may have gotten in at some work site that used it previously.

If you want to save money or avoid a prescription and use welding oxygen (which I have personally done) then here’s the solution: Buy a new welding tank and spray paint your name on it. When you get it filled/refilled, demand your personal tank back. Now you have chain of custody. The oxygen will be medical grade and since you started with a clean tank there will be no contaminants. Make sure that you don’t tell the refill station why you really want it or they may not refill it for you. If they ask, have your cover story, like welding…

Also, you will want a regulator that has a range of about 5 to 15 liters per minute. The oxygen that comes out will need to be controlled so you don’t waste it. Get one that has both liter-per-minute (LPM) and pressure gauges so you know both how fast you are using it and how much you have left. For medical applications, you don’t need 100% oxygen unless you are dealing with something like smoke inhalation or carbon monoxide poisoning. Raising the inhaled oxygen content from 21% (normal) to say, 50% will be a boon for your injured mates and make your limited supply of this valuable resource last longer. I would use oxygen with lung injuries or loss of blood, but this is a topic better answered by others.

You will also need to get/make an adaptor with the appropriate male nipple size to fit on the end of the regulator that will attach to the female end of the plastic hose that goes to the mask you will be using.

Welding regulators are not set up to go directly to a mask and medical grade oxygen regulators (which will go right to a mask hose) will not fit on a welding tank (by design to thwart this very thing).
Masks are inexpensive, but medical supply houses can be sticklers for requiring a prescription for them. Online purchases rarely require them. You will want what is called a rebreather mask. They look the the ones you see fall from the airplane ceilings in movies.

If you want to give 100% oxygen and not waste any, look at the rebreather bag attached to the mask. Decrease the LPM of oxygen until you see it deflate with each inhalation but not all the way. If it stays fully inflated at all times you are wasting O2, if it goes empty/flat on inhalations, you are dropping below 100% oxygen and forcing the patient to pull in extra air from outside the mask which not only decreases the oxygen level but may be difficult for the injured. If you want to go below 100% oxygen, then make sure that the mask has valves or ports on it to allow air to be breathed in from outside or loosen the mask a bit so air can get in from the sides. Test this by making a tight seal with the mask on your face, plug up the hose and breath in. If you can do this without effort, you’re set up is good. Don’t go with nasal cannulas as they waste 50% of the oxygen and you’re not likely to get a refill anytime soon.SF in Hawaii


Despite the dire warnings, there is no difference in oxygen purity or suitability for breathing among the four “grades.”

From a major supplier’s web site:

‘There are four kinds of oxygen that are merchandised or sold to users; Aviation, Medical, Welding and Research. There is a ongoing controversy if 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, we have been told by the suppliers of welding oxygen, 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.”

All oxygen is generated from oil-free compressors/liquefiers because any oil (of whatever nature) is highly flammable in 100% oxygen

The bottom line is safety – oxygen makes things burn, even people. Safe use requires scrupulous attention to cleanliness and detail. Don’t do it if you don’t know if it is safe or not. – JB, MD


I sent in a letter about using aviation or welding oxygen instead of medical oxygen and another reader replied, objecting that compressor oil could compromise the safety of the oxygen. I don’t want to get into a tit-for-tat over the subject, but I think it’s important to address the reader’s concerns because the lack of a prescription may keep people from obtaining oxygen that could later save a life.

Unlike SCUBA air, oxygen is not pumped with a compressor at the point of bottle filling. It is dispensed from a large tank that has been provided by a supplier like Air Products or Praxair. Oil, whether petroleum based or vegetable based, is not present in the compressed oxygen. Oil and grease can burn spontaneously when exposed to pure oxygen – especially under pressure – so the suppliers take care to remove such impurities before bottling.

When I said that medical, aviation and welding oxygen are all clean, pure and dry, I meant exactly that. They come from the same source! ABO, medical and welding oxygen are all U.S.P. grade oxygen and all are safe to breathe. The only differences among them are that ABO has had an additional drying step to prevent ice formation at altitude and there are slight differences in filling methods (evacuate first or not) and paperwork, all inconsequential when we’re talking about supplemental oxygen delivered through a mask or cannula.

Private pilots have been using welding oxygen for years with no ill effects. If welding oxygen somehow scares you then by all means, buy ABO: We know that’s safe to breathe. My main point was that there is a no-prescription option available.

I just Googled a good resource. This guy is an expert on the subject and perhaps his paper will clarify things and end further debate on this subject. – Matt S.

One Comment

  1. Oxygen is cracked from air, and then liquefied….To get the 2 grand plus pressure used in a bottle it IS run through a (very special) compresses and then into a manifold where dozens of bottles are connected and filled. – I a “real” gas supplier anyway. While you can get a bottle filled “on the spot” from a bank at a small rural supplier the normal way at an industrial supplier is just to exchange bottles that have been on the manifold the day before you got there.

    And NO there is no differance at all in the oxygen that goes into the bottles. It must be 99%+ pure or it will not work to cut steel with an Oxy Fuel cutting torch.

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