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Are you getting trimix and nitrox mixed up? 130 feet would be pushing it
for something like EAN32 (1.6 pp at 130). However, narcosis wouldn't be
that much of a problem due to the lowered nitrogen content. The lowered pp
of nitrogen would make the dive equivalent to ~110fsw (as far as narcosis is
concerned).
Trimix is generally never used shallower than 100-120 ft. Depending on the
mix you could die of asphyxia at shallow depths with trimix due to the
reduced oxygen.
-- Jason
At 09:20 PM 10/15/97 EDT, Hans Petter Roverud wrote:
>Somebody stated: Technical trimix is a deep air
>course. I believe he's right -- this course is
>definitely bordering on the "deep air" that most
>most of us agree to avoid.
>
>My deepest "technical nitrox" dive was a nitrox
>23 dive to 160'. Of course, 23% oxygen is
>a ridiculous mix since it's not worth the effort,
>but the point was to practice making EAD calculations. The
>purposes of "technical nitrox" are to learn gas
>management, practice swimming with a heavy rig
>and practice gas switches.
>
>My question to the board is, what do you think
>would be the preferred depth limit? We definitely
>do not need "level stoned" yet we do want a
>realistic task loading, deco obligation included.
>I would suggest 130' as a good target depth for
>"technical nitrox" -- it's enough to provide a
>realistic training scenario for future trimix divers, yet
>narcosis is not a problem.
>
>However, as a physiologist I know that narcosis
>can be measured at depths shallower than 100'. If
>we demand no narcosis whatsoever, we really have
>to pull back. What is a reasonable EAD for a
>trimix dive? Ask some and the answer is 200' --
>ask others and they go 100'. Ask me and you get
>100' - 130'. I believe the "technical nitrox",
>"extended range air" or whatever you call it
>should have a target depth matching the EAD you
>will prefer as a trimix diver. Learning the
>toting, configuring, switching and balancing
>the rig does not depend on going deep. Actually,
>some of the best training may be to swim
>sidemounts for an hour at 20'.
>
>I think most of the current philosophies are
>based on giving students a taste of narcosis
>and prove the need for trimix. I believe most
>of today's trimix divers have thorough
>knowledge of nitrogen narcosis from past
>experience.
>
>Discussing this with some friends,
>the opinion was voiced that past deep air experience
>might be an advantage. I half-heartedly
>disagree. Sure, it may be sort of an advantage
>to have been there and know what to avoid, but I
>don't think new trimix divers need to go
>through the same phase of trial and error. In
>retrospect, an advantage but no prerequisite, and
>definitely not the direct way to learn trimix.
>We need to build a record and gain experience
>underwater doing what we're supposed to do. If
>trimix is the tool of the trade, it makes a lot
>more sense to log more trimix dives than it
>does to practice deep (or even deepish) air
>dives.
>
>My conclusion: 130' is a good target depth for
>practicing and preparing for trimix. What do
>you say?
>
>
>
>
>
>--
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