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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 > > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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