Oxygen compatible air and O2 Clean myth
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Technically, if you decide to have put 36% nitrox put into a cylinder that is not oxygen clean, you do not take any consequences. The consequences are visited upon the person filling your cylinder when it blows up.
Of course, as I suggested, nitrox divers around the world violates this industry standard every day.
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That depends totally on:
- Whether or not you believe that anything above 23% requires full O2 clean procedures, which some standards do and some standards don't.
- Whether that 36% is mixed using PP blending or continuous blending (only applicable if your belief on point #1 conforms with option #2)
I can't remember a "nitrox" fire ever - although maybe they have happened during PP filling but it was reported as an O2 fire. Every example (in my head at least) is with a cylinder full or near full of 100%. So my gut is telling me that the 400psi added for PP fills is low enough pressure or its added on top of the remaining fill which acts as a diluent and there is a big risk reduction there. Compared to 3000psi of O2 being handled or released into a torturous valve and regulator flow path.
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Well, last time I checked a lot of the diving industry - including quite a few continuous gas blender manufacturers - have claimed that if you stay below 40%, you don't need to follow O2 clean procedures. IOW, your gas can be treated like air.
To be honest, I can't provide proper cites to that right now. But I do know that there's a certain... disagreement about that opinion.
Don't misunderstand--I think the CGA standards are ridiculous.
I think that is the real problem for scuba. Those standards are written by people who deal with the realities of compressed gas handling in an industrial world that has nothing to do with scuba. They are written for warehouses and workshops. In those environments, it is easy to meet standards like that, so setting standards to an extreme level is no big deal. Knowing this, I have to make decisions on which rules I believe are over the top.
For most of my technical diving, I have to bring my own mixing setup with me. I get bottles of helium and bottles of oxygen, and I load them in a cargo van. I drive 6 hours to the dive site. We mix trimix and nitrox in a motel parking lot. According to industry standards, those supply bottles need to be transported standing up. That rule is easy enough for most businesses, but not for me. I can't stand them up in a cargo van. When I go to the supply shop and get the gas, they help me load my van. They know the rules, too, and they help me violate them.
BTW this article was published in 2001.
That was back when "hyperfilters" were a thing, PADI, NAUI and the other big agencies didn't even allow nitrox. Nobody really knew what was what and there was no appreciation that you can EASILY make gas that's plenty clean enough for PP blending with almost any decent filtration system. I'm not even sure molecular sieve x13 existed for scuba filters back then. I wouldn't be surprised if silica was still in widespread use. Certainly hopcalite was almost never in use, CO was never measured, gas was infrequently analyzed, and gas was frequently very wet.
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