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> 
> 
> 
> On Thu, 5 Oct 1995, Roderick Farb wrote:
> > I neglected to say that the dives (200 feet, dark and 49
> degrees F) in 
> > France on the CSS Alabama were all done on air. Because some of
> the divers 
> > on the project are commercial divers working for MELOX, COGEMA
> and COMEX 
> > insurance regs. prohibit the use of helium in scuba tanks. So
> all 
> > several hundred diver-dives made in the past nine years have
> been done 
> > on air. Without incident. Their outstanding work has been
> published in 
> > numerous scholarly journals in France and the US.
> 
> Suffice it to say that you can dive 200 feet on air. 
> Professionals as in 
> this case do it not because they want to, but rather because
> legally there 
> is no other way. The problem that I see is that people who do not
> have 
> the proper approach to these kinds of dives tend to pay the
> ULTIMATE 
> price, their life. A little out of shape, a little too much
> exertion, a 
> little under hydrated and wham bam thank you mam!
> 
> When I first became interested in a cave dive that required a
> QUICK drop 
> to 250 with an excursion at 200 I asked people that I considered 
> knowledgable about diving about deep air. I asked why did so many
> people 
> seemed to do it with impunity? The response I got was that yes
> they did do it
> and you read about it, but did you read all about the many ones
> that 
> didn't live through it.  Something about "natural selection" at
> work.
> 
> With the recent spate of deaths at medium depths due to wrong gas 
> selection I think that the quote that might be appropriate would
> be
> "high PPO2s can be hazardous to your health".
> 
> Seriously, if the divers in question could have used trimix do
> you think 
> they would have used air? 
> 
> Safe Diving
> r.b.
> 
> --
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> 
> 
> 
> ---- End Forwarded Message
> 
> 
> 
> While there appears much vocal objection to deep dives on air,
> where the primary
> culprit is ppO2, we are reading about a large # of problems
> associated with divers
> attempting to maintain ppO2 within the magical limits.  They
> strive to achieve this
> via gas mixes switches, blends, etc. But they make errors, run
> out of appropriate mix, 
> miscalculate the proportions.  They perish.
> 
> Maybe each of those actions represent a failure point.  Gas
> mixing, its analysis, correct switching, etc.
> are all tasks, some performed under stress!  The more failure
> points, the greater the
> probability of failure.
>  
> With wrong mix, wrong composition, whatever, obviously the
> meticoulosuly careful will be
> less prone to such operator errors.  But operator error is
> claiming lives.
> 
> The question to ask is: are the groups that are not using these
> exotica experiencing
> less, more or about the same # of problems relative to those
> using the exotica, the task loading.
> Obviously not only must depths and durations be compared, one has
> to pair data based on
> conditions, etc.
> 
> A good case is the one posted by Mr. Farb.  Irrespective of the
> assaults on the practice,
> the outcomes seem to speak for themselves.
> 
> The NA wreck diving community has consistently dove under North
> Atlantic diving conditions
> on depths in the 160-200+ ft range.  Air was the only choice
> available for many years,
> and continues to be the predominant gas.  Fatality statistics do
> not appear to point the finger
> at O2 tox.
> 
> On the other hand deaths over the last few years in the NA where
> O2 tox have been implicated appear to be those where
> O2 was being employed as a deco gas or where nitrox was being
> used, possibly beyond its
> safe depth.   The inevitable question then is:  Would those
> deaths not happened if air was the only gas in use? 
> 
> It thus appears prudent to consider the other attendant problems
> of 'tech'
> diving, the tasks and failure points, before espousing it as the
> panacea of extreme
> exposures.
> 
> We can argue the virtues of keeping ppO2 < 1.4 all we want.  It
> may be that the problem lies elsewhere, in the actual act of
> switching to the 'correct' mix.  Or the actual mixing. 
> 
> Neither of them become an issue using a gas that does not require
> switching.
> 
> 
> 
> Esat Atikkan
> 



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