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>Hello, > I'm trying to put together a filtration system so we can began mixing >our >own Nitrox You don't say whether you are doing it commercially, or just for yourself. If you're doing it commercially, you'll probably want all the trick filters, just because the customer will expect them. If you are doing it for yourself, then you just have to do what you are comfortable with. A lot of us are starting to wonder about this whole super-super-clean air thing (at least for FO2's below 50%. There are a LOT of folk doing there own mixing, using standard dive air, and no one has been able to cite a single instance of anyone blowing up a tank or other unpleasantries without other factors being involved. Checking dive shops around here that don't do nitrox, I find that the better of them already pump air that meets the more realistic nitrox standards - like TDI's .01/mg3 - without having any extra filters. One final irony - those trick filters are easily wiped out, by too much moisture, among other things, and have a fairly limited life under the best of conditions. I've heard people in the industry say that many of them are functioning most of the time as window dressing, rather actually doing anything. If you read any of the studies done on this, you find the real concern isn't for the amount of hydrocarbons that can be delivered in a single fill of air, but rather, over long term build up in the air/mix system. Since in PP mixing, the only component that sees high PO2 is the tank, that's pretty easy to stay on top of, by inspection and cleaning as nec, especially since even a frequently used tank sees only a tiny fraction of the volume of gas that a compressor/mix system does. Using very slow fill rates is also cheap insurance against less than perfect air - remember, for combustion to occur one needs, not only fuel and oxidizer, but heat. Incidently, an old-time dive shop down the road has a filter system that consists of a 50 cf alu tank filled with loose activated charcoal and some sort of slightly trick valve/adaptor on top. He says this was standard practice when he bought the rig (1960?) and it works fine (but he didn't offer to show me any test sheets). By-the-book nitrox air requires multistage filtration, but one wonders if the priciple could be adapted, by filling the tank - or putting several in series - with the different agents needed rather than buying an expensive filter system, and then keeping it filled with expensive cartridges. Got a nice alu 72 you can have cheap if you want to explore this idea. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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