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What Is O2 Clean

Courtesy of Kathleen at Dive Rite

by Harry Avril

You probably know the story of the blind men and the elephant. If you somehow missed it, here's the short version:

Three blind men came upon an elephant. The first, feeling the animal’s leg, proclaimed that an elephant must be much like a tree trunk. The second, finding the animals trunk, said that a more apt comparison would be a snake. The third, holding on to the elephants tail, was puzzled by the first two’s misinterpretation of the facts. To him, an elephant felt exactly like a rope.

We see much the same confusion taking place over our new Modular Valve System (MVS) tank valves. These components come from the factory free of hydrocarbons and other flammable contaminants. The lubricants used in the valve assembly are non-combustible. The o-rings and seals are made from Viton or other oxygen-compatible materials.

Aha!" say the blind men, “These new MVS components must be much like the oxygen clean or oxygen service rated equipment we read about in textbooks."

Not exactly. This may, in fact, be a good time to open your eyes to the facts regarding oxygen cleanliness.

Oxygen Cleaning in the Big Leagues

When the aerospace industry needs a component “oxygen clean,” they do not simply take it out in back, hose it down with Simple Green and swap out a few o-rings. True oxygen cleaning takes place in a special “clean room,” whose atmosphere is free of dust and contaminants.

Once the component is free of hydrocarbons and other combustible elements, it is sealed within a sterile environment and never again exposed to normal atmospheric dust, moisture and contaminants. This is what it means to be oxygen clean.

So Are the Textbooks Wrong?

I say the word boat. You envision a rowboat. I'm thinking of the Queen Mary. Which of us is wrong? The problem here is a matter of semantics. (A term used to describe the process of using word meanings to prove that you're right and the other guy doesn't know what he's talking about.


If you are writing a textbook, you can get away with using a broad definition for oxygen clean and oxygen service. That's because textbook writers have yet to come under the scrutiny of America's insurance underwriters and trial lawyers. When you are a manufacturer or distributor, you are continually in the specter of "product liability." This holds you to a higher standard of accountability and motivates you to choose your words carefully.

So What Can we Say about MVS Components?

The broadest label we can apply to MVS components is to say that they are Nitrox ready. But wait--isn't all dive equipment suitable for Nitrox use when filled from a pre-mixed source? If the pre-mixed source is no richer than EAN 40 (40 percent oxygen), the answer is yes.

Okay. How about using MVS components in an "oxygen clean" cylinder in which you plan to do partial-pressure Nitrox mixing? Let's put on our tap-dancing shoes here.

When new, the latest generation of MVS components comes from the factory free of hydrocarbons and other combustibles. They use Viton and other oxygen-compatible O-rings and seals. They are not, however, assembled in a clean room or sealed in a sterile environment. Additionally, we have no control over what happens to the valves after they leave us.

As a result, labeling our new MVS components as oxygen clean or oxygen service rated (although they may appear to meet the most commonly used criteria among the technical diving community), is not accurate. The best analogy might be the futility of trying to determine whether a new diver is "safe." The fact is, once you give that diver his or her C- card, you have limited control over the diver's behavior or the choices he or she makes. Therefore, there is no way you can label such a diver "safe" or "unsafe."

The real problem, of course, has to do with the present legal climate in the United States. Makers of dive equipment are every bit as hamstrung as other manufacturers. So bad have things gotten that you can no longer claim that a BC might provide surface flotation, or that a dive computer might be used to avoid decompression illness.

Tort reform legislation recently passed by Congress may help; however, the real solution lies with individuals. If you want to participate in technical diving, you have a duty to educate yourself to the degree needed to make sound decisions-and, having made a decision, you must be willing to take responsibility for it. If you are not, you only stand to make diving so expensive that none of us can afford to participate.


Harry Avril