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Jason, It is clear that if you are tri-mix certified your instructor was a dope or you slept through at least part of the class. There is nothing that says the mixed gas should be hypoxic. For that matter it could well be hyperoxic. I have done a few "tri-mix" dives this summer in the 150'-170' range using a normoxic tri-mix with 25% He (see archives on marking tanks). It makes for a low END and keeps the PpO2 below 1.4ATA. I know of an Instructor who uses a 34% O2 15-20% He on some dives in the 100' range. No risk of anoxia with that gas don't you think? At 09:28 AM 10/16/97 -0700, you wrote: >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? >> >> >> >> >> >>-- >>Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >>Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. >> > >-- >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > > Bill (aquadart) Bott -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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