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So Mike -- lemme see if I got this right --- the training you recieved did not cover oxygen exposure where "air" breaks are needed ? Though they had you use EAN80 instead of 100% oxygen ? Agencies dont teach --- teachers do and teachers who also get out there and dive when not teaching do it even better. Nothing worse than a guy who is always in a classroom. As far as the stroke mix is concerened I addressed that a few posts back --- no need for is -- just use the correct deco mixes and life if easy. At 06:28 PM 11/24/1998 -0000, M.S.Langborg wrote: >No, as you know, all the "major" agencies teach deco using 80 %. > >Mike > > > >-----Original Message----- >From: Joel Silverstein <joelsilverstein@wo*.at*.ne*> >To: Mike Langborg <mslangborg@cl*.ne*> >Cc: techdiver@aquanaut.com <techdiver@aquanaut.com> >Date: 24 November 1998 02:08 >Subject: Re: 80% arrrgh!! was Re: On the left > > >>yup -- wasnt that covered in you training program? >> >> >> >> >>At 09:42 PM 11/23/1998 -0000, you wrote: >>>Ok, so 100% oxygen is the way to go. What do you do about "airbrakes". >>> >>>When, i.e. after 20/25min? >>>for how long, i.e. 5/10 min? >>>And what gas do you use for "airbrakes" i.e your 50%, your 36% or your >>>bottommix? >>> >>>Mike >>> >>> >>> >>>-----Original Message----- >>>From: Joel Silverstein <joelsilverstein@wo*.at*.ne*> >>>To: gwaw@ix*.ne*.co* <gwaw@ix*.ne*.co*> >>>Cc: Techdiver@aquanaut.com <Techdiver@aquanaut.com> >>>Date: 23 November 1998 16:23 >>>Subject: 80% arrrgh!! was Re: On the left >>> >>> >>>>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'. >>>> >>>> >>> >>> >>> >>Joel Silverstein >>Scuba Training + Travel Co. >>http://www.NitroxDiver.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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