[PSUBS-MAILIST] Commercial Grade O2 vs. Medical

[Sean T. Stevenson via Personal_Submersibles]

Industrial and medical grade oxygen bottles are both filled from the same bulk cryogenic storage tanks. The difference is in fill procedure. Medical cylinders have a vacuum pulled, are flushed briefly with oxygen at low pressure, have vacuum pulled again, and are then filled to capacity. Industrial cylinders may have one or zero vacuum steps prior to filling to capacity. All else being equal, general-purpose industrial oxygen and medical oxygen should analyze exactly the same. The medical grade, however, is routinely analyzed for CO and total hydrocarbon content, and a paper trail is created to ensure that the medical gas meets USP standards, hence the additional expense compared to industrial gas. Surprisingly, medical oxygen is one of the least pure grades available, with research grades to several nines purity available for comparable cost, because the paper trail for the non-oxygen component is not necessary. Also available in some locations is so-called "aviator's" oxygen, which is the same stuff again, but is analyzed and certified to contain near zero water content, to prevent freezing of oxygen systems in low temperatures at altitude.

Realistically, oxygen purity is critically important for divers who may be inhaling any contaminants / non-oxygen components at elevated partial pressures, with all of the physiological implications of that. For submersible atmospheres, which are both normoxic and nominally at normal atmospheric pressure, it is less critical. In a sub, you are exposed to contaminants regardless from other mechanical systems and materials in the habitable space. I wouldn't be concerned about industrial grade oxygen used in a submersible life support system, provided I had performed a basic analysis to confirm e.g. 99.5+% oxygen, and then had some means of charcoal or permanganate filter to remove any hazardous impurities in the cabin air.

Sean

-------- Original Message --------
On Jan 3, 2018, 11:10, Steve McQueen via Personal_Submersibles wrote:

> I tried to search the archives but it wasn't very friendly. Sorry to again ask about something I know has probably been discussed. I wanted to double ck. my O2 strategy. After some investigation it seems I will buy a new steel high pressure oxygen tank for external mounting. My plan is to have it refilled with "commercial grade" O2 vs. medical grade 02. As long as I keep my "personal" tank and not allow the filler to swap tanks I should create a "chain of custody" that will help me feel good about not having contamination. I am wondering how others are managing. Thanks, Steve _______________________________________________ Personal_Submersibles mailing list Personal_Submersibles at psubs.org http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
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