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From: Jan Werbiñski <janwer@fo*.co*>
To: <>
Subject: Re: What ppO2 for bottom mix?
Date: Fri, 18 Jul 2003 14:40:54 +0200
From: <Jsuw@ao*.co*>
> Not having a plethora of gas mixes makes things a lot easier when you mix.
If a dive gets cancelled or you don't use a cylinder for some reason, you
can always use >that gas on another similar dive, and you have a wider range
of those dives for that gas.  There is nothing worse than dumping a cylinder
containing trimix because you >
>need to mix a different gas for use in that cylinder.

I remember David Shimell on this list making his own list of custom mixes.
He have different bottom mix for each 10 meters range and corresponding
tables. Runtimes are in 5 minute and 5 metre increments. He have tables for
each mix already laminated.

Interesting alternative for GUE custom mixes, isn't it?

> The limit has steadily dropped and dropped (from 2.0 to 1.8 to 1.6 to 1.4
and now 1.2).  I don't really care if other agencies are promoting practices
I consider unsafe, >or at least, more risky than necessary.  I like the 1.2
limit on PO2 because I want to avoid CNS O2 toxicity and I want to off-gas
properly during the dive and during the

Is those limits dropping because more people involve in tech diving? More
people with poor physical and mental shape who should not dive deeper than
recreational level? Maybe because of this people is limits changing?

I'm really interested in seeing statistics showing: amount of divers, amount
of dives, amount of oxtox cases for each ppO2. Does it exist?

> > Well, actually I felt the difference having 23% He...
> > ...nitrogen narcosis, and can detect it without problem.
> I did goof here when I mentioned 35% helium as a minimum.  I use 30/30
trimix for recreational depth dives, and I do feel the advantage of the 30%
helium even on these kinds of dives.  I am definitely less narced, and I
feel less decompression stress than when I dived air or nitrox in the past.
> Narcosis is insidious; its early effects are subtle and occur shallower
than you'd imagine.  I doubt you are completely aware of when you are
narced.  Expect that you >are at least mildly narced even at 30'.

Agree. Shallowest depth I felt obviously narced was 17 meters - stress of my
first drysuit dive.
Well, next time I'll try to use higher fraction of helium and see for

> > ...Why to add 5 minutes for gas switch?
> The five minutes allows the deco gas to completely circulate from the
lungs all through the blood.  You want the window of time for this to occur
during the deco.

Is is a standard procedure or your own? I heard about 1-2 minutes to add for
a gas switch or waiting until next full minute on computer etc.
Should I include this 5 minutes only during ascent or also in switch from
travel to bottom on descent?

> Besides traveling to dive, I arrange occasional recreational and tech
dives in my own backyard, offering my friends lodging at my place.  That's
because the warm >
>water ocean dives are at my doorstep here, as long as the winds are
favorable.  They come from Tennessee, north Florida, Michigan, etc.

Lucky you. :-)

> Please let me repeat my advice from before:  Look at the and web sites at the articles there on decompression, using helium,

I know those sites already and noticed late changes.
Thank you. I'll try to use some of your advices.

Jan Werbiński       O0oo....._[:]) bul, bul, bul
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