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
> >--
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> >
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