Posted by tleemay on January 04, 2001 at 18:08:33:
In Reply to: Re: The view from here posted by Max Bottomtime on January 04, 2001 at 16:21:54:
First off Max, I'm not trying to flame you or
anyone else - I just cannot see the rationale
for diving deep on air when something better
and safer is available. This discussion is
treading into the tech diving realm, which is
how you describe yourself - and you used the
"S" word, not I ;-).
Max wrote:
"Would the proper mixes make my dives safer?
Absolutely."
Then we all agree that diving the proper mix for
the proper depth and safer ppO2 is a good thing
... let's continue.
Max wrote:
"If I had unlimited funds, I'd be using a trimix
rebreather. Unfortunately, I'm just another poor
California dive bum spending a couple bucks to
fill my tanks with...AIR!!!"
How much do you value your life and the experiences
you would have at those deep dives on air? Let's
forget at this time the solo and heavy steel tanks
in a wetsuit, and your rebreather issue.
How much value do you place on your life on being
safe at say 160' on air? The cost of $8 worth of
air, or even $0 if you drive to Bevery Hills? I
have heard the arguments before and read the
research over deep air. There are many out here
that say things like "I don't need to use trimix,
I am good on air" or "I've built up a tolerence,
so the narcossis that affects everyone else doesn't
apply to me". The N2 (and O2) narcosis effect is
like driving drunk. Bernie Chowdhery ("The Last Dive"
and "Immersed" founder) perhaps said it best in
that for every 33 feet a diver ascends to depth the
effects is like becoming intoxicated on one martini.
At 200', a depth that most deep air divers limit themselves to, that's in effect like
diving with over 6 martinis consumed. There are
people out there that feel they can easily drive
drunk with 6 martinis in them - and they might get
lucky and not get injured or killed on the way home.
But eventually the odds will catch up with them.
In my opinion as well as many experts, the same
goes for diving. You can make many many dives deep
on air and not once have a problem. Then one day that
major CF of a problem comes along where you will
require every bit of your cognitive skills to pull yourself
- or your buddy - from an even more perilous situation
than just being 200 underwater. The Rouses dove
air to 230 feet for only 11 minutes to have a
problem that warranted, rather demanded a clear
head and reduced narcosis. The proper gas could
have kept them alive and coherrent until which
time they could have gotten out of their eventual
deadly situation. They though they were good on
air too.
Now how much value do you place on your life
breathing the correct gas, say a 160 ft dive
for 20 min? Let's apply something normoxic like
a 21/25 mix. For that depth and time that's a ppO2
of only 1.23 - so O2 tox really is remote. The
END of that mix at depth is about -97.1, so even
though your body is at 160 for that finite amount
of time, it thinks and essentially behaves like it's
breathing at less than 100. You would have a
cleared head, be able to react and think quicker,
and feel better after the dives - especially if
you did more than one of that type that same day.
Add to that the reduced damage the He is causing
to your tissues compared to the N2 over a cycle
and there some long term benefits too.
There is obviously a decompression cost diving
that particular mix at that depth for that time -
stops at 80-1, 70-1, 60-1, 50-2, 40-3, 30-4,
and the big one 20-34. That's a total run time
of 69 minutes.
Now, if you introduce O2 to accelerate the deco
schedule at the top 20' stop, your profile would
be greatly reduced with the stops being the same
until 20', then it's decreased to 11 minutes, or
a run time of 46 - that's cutting 23 minutes out
of the deco obligation. A 40 cft bottle of O2 runs
about $18 and could be used a couple of times for
this type of short time use.
The cost for this benefit and added safety, about
$29 for two steel 95 rated at 2400. If you are diving
the even heavier 112's or 104, the cost will approach
the $36 range.
On straight air, the same dive would have required
you to do stops at 80-1, 70-1, 60-1, 50-2, 40-3,
30-4, and a whopping 32 minat 20 for a total run
time of 66 minutes. That's 3 minutes longer than
the 21/25 mix in total, but you would be suffering
the effects of narcosis and losing your safety edge
and clear recall skills. Obviously the best would
be to utilize the O2 and keep the entire run time
down to 46 for this profile.
These are just a general example of one profile,
but I hope you,a nd anyone else, understands what
I'm trying to say here.