Hans, we believe as you do. We have a "starting" point of 130 aed and
1.4 ppo2 maximum. This is calculated to the deepest depth we are
expected to encounter, even though the "profile" is problably less. We
then reduce the ppo2 for the longer exposures, and raise the helium for
more precise work. Effectively, we end up diving more like 1.0 ppo2 and
less than a 100 aed. Jarrod, Brent and I are actually diving as low as a
..6 ppo2 and a 60 foot aed in some cases. I do the survey and the
mapping, so I dive the highest helium, in many cases approaching heliox.
I feather this in, diving a lower helium and higher oxygen early in the
dive and then a higher helium and lower oxygen later in the dive ,
bringing the ppo2 up at deco, but stil no spikes. I have no haskel, so
get the higher mixes by lowering the pressure, or running the helium
through my compressor. I generally dive lower pressure on my back gas
(to prevent reg failure), and have more in the stage bottles, where a
reg failure is insignificant since I can manually operate the tank
valve.

 What all of you will find, as I did per force, is that the higher
helium, lower oxygen mixtures are much more pleasant to dive on, and
really onlly incrementally more expensive than helium at all. Oxygen is
dirt cheap here. 

 We found a lot of this out by accident, since we dive helium so often,
and do so much decompression diving, we are not afraid to experiment
with gas. We end up blowing air on odd gasses and diving them shallow,
rather than dumpingn the gas, and have even done some trimix dives at
Ginnie Springs. I did that one on 18/40 ( air blown back onto a
12/55)one day and really liked it. 

 Our oxygen maximums come from commercial diving ( and I do not mean
cleaning the bottoms of boats, I mean oil company diving). We use a
maximum level for ppo2 at or below which seizures are not expected to
occur using previous datalines. The helium we have gradually changed our
thinking on as we discover impairment in different ways, and as we
realize that it is in fact a more friendly gas to decompress from than
nitrogen. The Germans found impairment is effective at all depths, and
this not only makes intuitive sense, it explains an awful lot of
unexplainable accidents . 

 If you want to experiment, breath some heliox in your living room and
read the newspaper - see how fast you can read and still comprehend
everything. Personally, I would like to see my kids take their  SAT
tests on heliox.

 Let's remmber that we are talking technical diving, and that the WKPP
represents the logistical sophistication and logical perfection of that
discipline, and we do it in ways that every last one of you can
immediately implement by adopting our way of thinking and attitude about
diving, and rejecting the ego threat and peer pressure of the air or
deep air equvalent depth crowd who falsely belive theri is some
"ability" to operate impaired. Did you ever hear the term, " he can
really hold is liquor"? That is a euphmaism for an alchohlic - only a
drug addict would need to "hold" a drug. Call me a weenie, but cakewalk
160 long range deep mixed gas cave exploration dives first - we must
know something. The deep air guys have ZERO of these dives, the high AED
guys have ZERO of these dives. Helium is the best thing that ever
happened to diving .


Hans Petter Roverud wrote:
> 
> At 14:36 16.10.97 -0400, you wrote:
> >Trimix does not neceassarily mena reduced oxygen. Where does this stuff
> >come from? - G
> 
> I don't know about Jason Reese, except that he got it wrong and was
> corrected. Apart from this nobody has really replied to my question: what is
> a sensible, productive equivalent air or nitrogen depth?
> 
> (Note: I believe oxygen is probably as narcotic as nitrogen. Thus, I use EAD
> rather than END. Whether this is right or wrong remains to be proved. If
> wrong it means a slight overkill only).
> 
> Who am I? A Norwegian IANTD certified trimix diver and nitrox instructor. I
> started diving in 1980 and have logged about 1200 dives, many of them "farm
> animal stupid" New Jersey style wreck dives. I switched to trimix two years
> ago and will not resort to "wah - wah" diving again. I'm sure we agree that
> many divers accept way too much nitrogen. It's like: We've been deep on air,
> and we want to go even deeper on mix. Since we used to survive 200'+ air
> dives, let's design our trimixtures to match air at 200'!
> People get narced. It's not lethal per se and there's still a lot of macho
> stuff about handling it. Thus, many divers will not admit to being affected.
> The treacherous thing about it is that you may look OK, feel relatively OK
> and have uneventful dives as long as nothing unforeseen happens. However,
> you're definitely not "all you can be" -- you lose out on a lot of things to
> see and you're not a reliable buddy if things go bad.
> Let's snap out of this and dive sober! There's so much to see and experience
> underwater and it's a waste of time to work on discerning it thru a haze. To
> me trimix makes a profound difference from 130'. I may think I see it all on
> air, yet when I switch to mix my field of vision broadens and the contrast
> improves. The dark shadows open up and reveal details I didn't know was there.
> 
> I'm about to finish a thesis on diving physiology. I ran chamber dives on
> air and nitrox 40 to look at mental performance during and after exposures.
> I did the practical experiment at the university of NY at Buffalo and I'm
> presently back in Bergen, Norway looking at the data. The main point is to
> look at post dive fatigue and assess whether it's directly related to inert
> gas load.
> 
> I'd like to learn what equivalent air/ nitrogen depth the WKPP aims at when
> diving trimix. Is 130' acceptable to you or do you go even lower?
> 
> regards
> 
> Hans
> 
>
--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]