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Mike, The standard answer would be to take a 5 minute break for every 20 minutes of O2 deco. If your deco is 20 minutes long, put the break halfway through, and don't count it in your deco time. Some divers doing extended O2 deco will break after an even shorter time than 20 minutes. It would be great if George or Bill Mee or JJ or any of those guys would explain how they manage breaks, I don't want to repeat it inaccurately...... Nanci t 09:09 PM 11/24/98 -0000, M.S.Langborg wrote: >Since I am not disagreeing with you, is this your way to say: I don't know >either?? > >Mike >-----Original Message----- >From: Joel Silverstein <joelsilverstein@wo*.at*.ne*> >To: M.S.Langborg <findir@an*.co*.uk*> >Cc: techdiver@aquanaut.com <techdiver@aquanaut.com> >Date: 24 November 1998 19:46 >Subject: Re: 80% arrrgh!! was Re: On the left > > >>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'. > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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