One of the most common discussions and questions I see in the ozone groups is about what oxygen to use with ozone generators. And as with everything, there are various opinions. That's fine, everyone has a right to their opinion. But here's the thing: we shouldn't present our opinions as solid facts, especially when official standards exist that we can point to.
So let me point to them.
What the Standards Say
The reality is that if we go by the actual regulations, industrial oxygen has a higher minimum concentration than medical oxygen. That's not my opinion, that's what the standards say.
Industrial Oxygen, CGA G-4.3 (Commodity Specification for Oxygen)
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Minimum purity: 99.5% (Grade A)
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Moisture: ≤ 40 ppm
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CO₂: ≤ 300 ppm
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Hydrocarbons: ≤ 10 ppm
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Source: CGA G-4.3
Industrial Oxygen, AWS (American Welding Society)
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Minimum purity: ≥ 99.5%
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Moisture: ≤ 50 ppm
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CO₂: ≤ 300 ppm
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Source: AWS standards for oxygen used in cutting and welding
Industrial Oxygen, EN 14704 (European Standard)
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Minimum purity: 99.5%+
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Moisture: ≤ 50 ppm
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CO₂: ≤ 300 ppm
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Source: European industrial gas specifications
Industrial Oxygen, GOST 5587-81 (Russian Standard)
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First grade: 99.5%
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Technical grade: 99.2%
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Source: Russian industrial specifications
Medical Oxygen, USP 32-NF37 (United States Pharmacopeia)
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Minimum purity: ≥ 99.0%
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Moisture: strict limits
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CO₂: strict limits
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CO: ≤ 2 ppm
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Source: USP Monograph
Military Oxygen, MIL-O-27201F
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Technical grade: ≥ 99.0%
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Aviator's grade: ≥ 99.5%
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Special high purity: ≥ 99.8%
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Source: US Military specification
So if we're being honest and basing ourselves on the actual standards, the industrial specification requires at least 99.5% purity. The medical specification requires 99.0%. The industrial standard is higher.
In reality, both are basically the same. The oxygen comes from the same production process, cryogenic air separation, at the same facilities run by the same companies (Linde, Air Liquide, Air Products). The difference is in the paperwork, not the product.
The Contamination Myth
I've also heard the argument that industrial tanks can get contaminated because when one gas runs out during welding, another gas can backflow into the tank. That's not true. There are safety valves specifically designed to prevent backflow contamination, and these are not optional equipment, there are OSHA regulations that require them.
So the idea that an industrial oxygen tank is somehow "dirty" or "contaminated" because it shares a workshop with acetylene or other gases, that's not how it works. The safety infrastructure exists precisely to prevent that.
The Practical Reality
Here's where I land on this: I don't care which oxygen you buy. Use whatever you have access to. But let me tell you what the practical difference actually is in the United States:
Medical oxygen requires a prescription. You can't just walk into a store and buy it. You need a doctor's order.
Industrial oxygen does not require a prescription. You can buy it from any welding supply store.
So when someone tells you that you "must" use medical oxygen for ozone therapy, ask yourself: are they basing that on the standards, or on an assumption? Because the standards say industrial has equal or better purity, and it's significantly easier to obtain.
Could Something Go Wrong?
Could there be some particular shop that filled a tank incorrectly? I don't doubt it. But the same thing could happen with a medical oxygen tank. Human error exists everywhere. The solution isn't to restrict yourself to one type of oxygen, it's to buy from reputable suppliers regardless of which type you choose.
The Bottom Line
Our opinions should be based on facts and standards, not on stories and fables that circulate around the internet. The standards are clear:
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Industrial oxygen: 99.5% minimum purity
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Medical oxygen: 99.0% minimum purity
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Same production process
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Same companies making both
Use whichever one you can get. Just buy from a reputable supplier. And the next time someone tells you that industrial oxygen is "dangerous" or "inferior" for ozone therapy, ask them to show you the standard that says that. They won't be able to, because it doesn't exist.
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This article represents the author's informed opinion based on publicly available regulatory standards. Always consult applicable local regulations and a qualified professional for your specific situation.