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Hey Trout, Good point ---- but ..... that may not be common all around -- i do haskel oxygen as do many ---- Oxygen cylinders should be dedicated to Oxygen only --- then you never need to worry whats in it --- (though you should always worry) At 02:29 PM 11/23/1998 -0600, Jesse Armantrout wrote: >maybe this one is common sense, but I've not seen it posted before... > >Another reason for liking 100% is that when I turn a bottle on and see 3000 >psi, I know that isn't oxygen. (I don't Haskel o2) This gives me a warn >fuzzy feeling. > >Trout > >---------- >> From: Nanci LeVake <nlevake@pi*.co*> >> To: Joel Silverstein <joelsilverstein@wo*.at*.ne*>; >gwaw@ix*.ne*.co* >> Cc: Techdiver@aquanaut.com >> Subject: Re: 80% arrrgh!! was Re: On the left >> Date: Monday, November 23, 1998 2:36 PM >> >> >> Arnie, >> >> Something Joel forgot to mention is that if you need O2 for a medical >> emergency, and you are using 100% O2 for deco, you already have the right >> gas there with you. >> >> Nanci >> >> >> At 10:14 AM 11/23/98 -0500, Joel Silverstein wrote: >> >Dear Arnie, >> > >> >It is quite easy to pump 100% oxygen to 3000 psi -- the dive shop needs >to >> >make the investment in a proper oxygen service rated Haskel Gas booster. >> >Most any reputable dive center who is mixing gas for the consumer should >> >have one, anyone that does not should step up pet the pony and buy one. >> > >> >80% EAN was not created from a decompression standpoint it was justified >by >> >those who did not have a gas booster. Here's why. Oxygen gets delivered >in >> >2400 psi bottles, (some major cities have gas suppliers who can supply >at >> >3500 psi) however you can cascade into a 3000 psi rated cylinder about >2250 >> >psi of oxygen top up to 3k with air and you have 80% oxygen content. >Simple >> >enough. However ....... >> > >> >80% EAN limits you severely. 1. at 20 and 10 fsw its PPO2 is too low >make >> >it useful, at 40 fsw its too high for maximum exposure limits. >> > >> >10 fsw 1.04 po2 too low >> >20 fsw 1.28 po2 too low >> >30 fsw 1.53 po2 borderline >> >40 fsw 1.77 po2 too high >> > >> >Where as 100% oxygen is >> > >> >10 fsw 1.30 po2 >> >20 fsw 1.61 po2 >> > >> >(with the 10 fsw stop normally being taken at 20 fsw >> > >> >Advocates of the EAN80 (a/k/a stroke mix) have come up with a variety of >> >reasons to justify not using 100% oxygen --- one of the great ones is >"its >> >good for divers who have trouble holding buoyancy at 10 and 20 fsw" >> >frankly if a technical diver cant hold a 20 fsw stop --- they should go >> >bowling and get the hell out of the water. >> > >> >Most divers who are using accelerated decompression tables have >> >standardized on their decompression mixes. (some are finding that >> >hyperoxginated heliox mixes are working well too though that is beyond >the >> >scope of this email) >> > >> >EAN 36 from 110 fsw >> >EAN 50 from 70 fsw >> >100% oxygen from 20 fsw >> > >> >Granted when you run one of the consumer dive profiling softwares you >may >> >see only a small decrease in decompression time -- maybe 5 minutes by >using >> >100% over EAN80. and though you may belive that is not a significant >enough >> >advantage to make sure you have 100% oxygen here are a few more >> >non-scientific reasons. From a mixing standpoint unless you are using >> >exceptionally clean hyper filtrated air or air produced from an oil free >> >compressor there is risk of explosion when mixing high pressure air on >top >> >of 100% oxygen. It probably has not happened yet --- but some day some >> >goober will blow up a building doing it. Even if you are using a 30 >cuber >> >(small) just cascading 2400 psi oxygen in it will give you 24 cuft of >> >oxygen -- for deco thats easily 40 minutes worth, which is a lot of gas. >No >> >need to goober around making EAN80 for the other 6 cuft, its just too >much >> >work for it and I am sure it costs a bit more, besides if you are doing >a >> >dive that requires much more than 40 minutes of oxygen decompression you >> >would want a bigger tank. The fact that a tank has a pressure rating of >> >3000 does not mean you have to fill it to that level. I have an >excellent >> >tank chart for all currently available tanks in the US on our web site - >go >> >look at it. Next; most consumer available oxygen analyzers using >> >electrochemical sensors can be off by as much as 2% in their readings, >so >> >is your 80% really 80 or is it 78? Whereas pure oxygen is upwards of 99% >> >pure -- it's a known item. >> > >> >Arnie, as a techie in training you have an opportunity right in front of >> >you. It's two roads ... the left road is filled with exploration, >> >friendships, technology and long proven safety procedures. The right >road >> >is bumpy, full of mis answered questions, body bags, and strokified >> >convolution. I get the feeling your want to take the high road and do it >> >right. In Judaic studies we are taught to ask why not to follow blindly. >> >So in this very long winding response (If I had more time it would have >> >been shorter) the answer is .... EAN80 buys you 6 cuft more gas, but >buys >> >you nothing else. Take no shortcuts when it comes to technical diving. >> > >> >Good Luck >> > >> > >> > >> > >> > >> > >> > >> >At 10:21 PM 11/22/1998 -0800, you wrote: >> >>Joel, >> >> >> >>Another question for you. It is prompted by your post on the bottle >> >>marking issue. >> >> >> >>What is the advantage of 100% O2 compared to 80% O2. I've been using >> >>the latter for deco. For one, it is somewhat easier to get at local >> >>dive shops because it is harder to pump the 100% to 3,000 psi, but that >> >>is merely convenience. More importantly, I can get on the 80% at 30ft >> >>and have the advantage of breathing a higher gradient gas mix sooner >> >>than waiting to the 20ft stop. The published tables I've seen give no >> >>time advantage to doing deco on 100% over 80%. >> >> >> >>What is your view and why? TIA. >> >> >> >>Blow gentle bubbles, >> >> >> >>Arnie >> >>Tech Diver in Training >> >> >> >Joel Silverstein >> >Scuba Training + Travel Co. >> >http://www.NitroxDiver.com >> >-- >> >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >> >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. >> > >> -- >> Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >> Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > Joel Silverstein Scuba Training + Travel Co. http://www.NitroxDiver.com -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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