Training for "Recreational Trimix"?
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Hatul
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What about using normoxic trimix (21% O2) ?. That would be an easy transition for a recreational diver? Main obstacle would be cost?
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Most "recreational" trimix has a slightly higher O2 content, 25/25 or 26/17 are 2 examples. This provides a slightly longer bottom time vs 21%. Similar to EAN 25. So a 120ft dive has a ~15minute "no deco" time instead of the 10 minutes you would have on air.
rx7diver, you really can't be talking about CESAs as a viable emergency strategy from >100ft. I know plenty of people here still reference this technique as viable from deeper depths - its not. The risk diving recreationally/no deco at >100ft is from your emergency ascent strategy not from the gas mix you've chosen. Despite having some helium which is a "faster" gas; doing an excessively fast ascent from 120-130 on 25/25 after a 10 or 15 minute "no deco" exposure is not going to hideously bend you any more than a similar ascent might on air or EAN25.
The embolism risk is the real problem and that's a consequence of running out of gas at depth and doing a CESA. Doing a practice CESA in class is one thing. In the real world people forced into CESAs by running out of gas frequently die because they take their last breath and hold it (in a panic) while doing the CESA. Don't worry so much about the helium "risk" and worry about the unviable CESA plan.
DuboisP
Contributor
narcosis at 135 foot ?
is it a joke ?
dive, dive, dive, and you will not
is it a joke ?
dive, dive, dive, and you will not
Narcosis at 135 feet is not a joke.
I have made three potentially lethal errors while cave diving at 100 feet. These errors are atypical of me, and the worst thing is that I was totally unaware of making them. Had I not been with a buddy whose brain was working better than mine, we could have been in a world of hurt.
As I have said a lot of times, narcosis is not being drunk off your butt. Narcosis is slow processing, slow reactions, poor decision-making, reduced situational awareness, and all of these occurring in a diver who may be (and often is) totally unaware of them.
There is also the memory thing . . . I had a fascinating experience in the Red Sea, diving the wreck of the Numidia. The first day, I dove it on Nitrox, and went to 100 fsw to look for hammerheads. I thought the wreck was really boring, because it was all dead coral and grey metal, and had no color at all.
The following day, I did a tech dive on the same wreck on 21/35, and I was astonished at the amazing color and the profusion of life I saw, some of it right in the same areas I had dived the day before. That afternoon, I did the wreck again on Nitrox, and it was back to being dull. Now, do I think it was dull when I looked at it? Probably not, but if I can't remember the colors, then they weren't very real for me.
Does everybody suffer as much from this as I do? Fairly clearly, the answer is no. But if someone WANTS to look into using some helium to think better and remember better in the deeper recreational range, I say, more power to them.
I have made three potentially lethal errors while cave diving at 100 feet. These errors are atypical of me, and the worst thing is that I was totally unaware of making them. Had I not been with a buddy whose brain was working better than mine, we could have been in a world of hurt.
As I have said a lot of times, narcosis is not being drunk off your butt. Narcosis is slow processing, slow reactions, poor decision-making, reduced situational awareness, and all of these occurring in a diver who may be (and often is) totally unaware of them.
There is also the memory thing . . . I had a fascinating experience in the Red Sea, diving the wreck of the Numidia. The first day, I dove it on Nitrox, and went to 100 fsw to look for hammerheads. I thought the wreck was really boring, because it was all dead coral and grey metal, and had no color at all.
The following day, I did a tech dive on the same wreck on 21/35, and I was astonished at the amazing color and the profusion of life I saw, some of it right in the same areas I had dived the day before. That afternoon, I did the wreck again on Nitrox, and it was back to being dull. Now, do I think it was dull when I looked at it? Probably not, but if I can't remember the colors, then they weren't very real for me.
Does everybody suffer as much from this as I do? Fairly clearly, the answer is no. But if someone WANTS to look into using some helium to think better and remember better in the deeper recreational range, I say, more power to them.
I have a buddy... accomplished diver with lots of wreck dives under his belt... several in the 90 - 100 metre range. He works in medicine, which in and of itself is irrelevant but it does lend a certain degree of self-analysis and scientific method to his behavior. More than a decade ago, he realized that his threshold for narcosis in cold water (Great Lakes) was somewhere around 21 - 25 metres. And that is what he mixes for.
70 - 75 is my depth limit on Nitrox in caves now. I can't feel the impairment, but I'm sure it's there.
Diving Ginnie on 30/30 last May was an amazing experience. I enjoyed it far more than I had ever enjoyed a dive there before. Wish I'd done my Cave 2 on helium.
Diving Ginnie on 30/30 last May was an amazing experience. I enjoyed it far more than I had ever enjoyed a dive there before. Wish I'd done my Cave 2 on helium.
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So here is just one more thing for us to argue about 
What is worse....Diving while seriously narced at 140 feet deep--OR, having a friend give "this diver" a 21/30 mix with the instructions to "dive it with the free V planner tables", and to make sure you perform a slow ascent?
If "this diver" is a good diver that NEVER has ascent speed problems, and can hold stops with ease and perfection....then are they a candidate for this--if they had the right friend.....OR, should the friend perfer seeing "this diver" doing the 140 foot dive and being stupidly narced?
What is worse....Diving while seriously narced at 140 feet deep--OR, having a friend give "this diver" a 21/30 mix with the instructions to "dive it with the free V planner tables", and to make sure you perform a slow ascent?If "this diver" is a good diver that NEVER has ascent speed problems, and can hold stops with ease and perfection....then are they a candidate for this--if they had the right friend.....OR, should the friend perfer seeing "this diver" doing the 140 foot dive and being stupidly narced?
waterpirate
Contributor
The old school aproach would have been to address the helium in a maximum 20%, and dive with tables not cut for HE. At 30% things become more critical. Friends do not give friends gas they are not squared away for, nor do they encourage people who still use " blow and go " as a problem solver to use HE.
Eric
Eric
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I'm fine diving an existing line to 90-100ft or so. I haven't done Ginnie but I didn't find the JB of a few years ago that brutal of a combination of depth and CO2. However, I know that my survey is crap at an END of 100ft and it takes me two dives to accomplish what I can do in 1 dive with an END of ~70ft.
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