Reason for Rec Triox?

[lamont]

I've never done it so I can't speak from experience. But, from what I know, the Yukon bottoms out at 100 ft. Based on how some of the DIR folk do their dives, if you had an average depth of 90 ft., your min deco limit would be 35 minutes assuming you are diving 32% (and from what I have heard, 30/30 uses the same limits). Seems like plenty of time to go exploring inside the wreck - 10 minutes in, 10 minutes out, 15 minutes buffer.

we did that exact plan on the saskatchewan and cape breton in canada earlier this year as well.

 

[KMD]

I don't think a penetration dive on the Yukon is going go be non deco unless you're only poking inside a outer area. Anything beyond that will probably require deco.

You could easily do a 30 minute penetration (15 in 15 back) and stay within NDL

Quote:
It also reads as though you somehow expected a difference in narcosis effects between air and nitrox. I don't think there is any evidence to support the idea that nitrox reduces narcosis.

Less nitrogen means less narcosis, right?

Not really. Some people consider Oxygen as narcotic as nitrogen. For END calculations people have used END = (1-FHe) * depth.

 

[MikeFerrara]

Less nitrogen means less narcosis, right?

I think the general consensus is, no. Based on lipid solubility, oxygen should me more narcotic than nitrogen but some of it is matabolized.

Maybe tolerance isn't the right word, but people can condition themselves to dive deeper on air. Bret Gilliam was doing 300' air dives regularly and functioning enough to stay alive. I know about others that dive those same depths on air with minimal to no narcotic effects. So, even though the studies don't show this to be true, real life examples do. Maybe I wasn't thinking as clearly as I would be if on helium, but I'm pretty sure I could have handled any problem I was confronted with.

Those real life examples don't show a tolerance. They show that it's possible to dive narced without getting killed. Lets face it, on lots of dives you don't have to do anything but swim around for a while and you don't need to do a lot of thinking to pull that off.

 

[Meng_Tze]

What the people who claim to have built a "tolerance" to narcosis are describing is probably a real effect that after a lot of experience diving with narcosis that it affects their dives less. It isn't really tolerance though.

I would call it mental tolerance. It is probably not physical, but definitely mental tolerance to the state of mind experienced while diving narced.

 

[TSandM]

Maybe I wasn't thinking as clearly as I would be if on helium, but I'm pretty sure I could have handled any problem I was confronted with.

I think my Fundies instructor's story shows that you can think you can handle anything, but when it actually happens, you may find out you can't. The most chilling thing about that story, to me, was the fact that he had no idea at the time that he was so narced he was turning a valve the wrong way.

There are some interesting studies in the Rubicon Foundation archives about narcosis and adaptation. One of the ones I thought particularly fascinating was one that showed that people could actually learn some tasks faster when narced . . . but they couldn't remember what they had learned when they returned to the surface. At any rate, no study shows any adaptation effect in terms of being able to cope with the unexpected.

I don't like narcosis, and for me, the thought of being a hundred or more feet underwater and having something go wrong when I'm three sheets to the wind doesn't sit well.

 

[MikeFerrara]

In any case, one's willingness to except the risk of some narcosis is one thing. GUE includes helium in the rec triox course because it's a tool that can be applied to dives in that depth range. Then the diver has the option.

The other end of the spectrum is how it was when my wife and I came up through our tech traiing. We did 170 ft training dives on air before we ever got to a trimix course and had the option. We did those dives, we lived and now we know for a fact that my wife's head turnes to mush at 170 ft on air so we don't do it anymore.

 

[dumpsterDiver]

I took my wife to 170 on air once. The Nikon SB 103 strobes both creaked audibly and then my wife's over-pressure valve failed on her BC. She was falling down along the wall, sinking, trying to swim up and was blasting air into the BC without having any clue that all the air was just escaping from the top of the BC. She was very surprised when I took her hand off her inflator, grabbed her and starting over-filling my BC to get our ascent started.

It was an otherwise uneventful and enjoyable dive, but it was clear to me that her situational awarness was very seriously compromised at that depth and that a minor gear problem could be a big deal. She had previously functioned well at 130-140, even on night dives, but after about 160 ft I think everyone is pretty compromised.

 

[Dive-aholic]

I think the general consensus is, no. Based on lipid solubility, oxygen should me more narcotic than nitrogen but some of it is matabolized.

Oxygen Narcosis: Fact or Fiction

Those real life examples don't show a tolerance. They show that it's possible to dive narced without getting killed. Lets face it, on lots of dives you don't have to do anything but swim around for a while and you don't need to do a lot of thinking to pull that off.

Granted, Gilliam's dives were basically bounce dives for deep air records, but I have heard of divers that still dive deep caves on air.

The other end of the spectrum is how it was when my wife and I came up through our tech traiing. We did 170 ft training dives on air before we ever got to a trimix course and had the option. We did those dives, we lived and now we know for a fact that my wife's head turnes to mush at 170 ft on air so we don't do it anymore.

I haven't been beyond the 140s on air and don't know if I ever will. There's a lot of conflicting information on deep air diving, and I don't expect those who do it to post it. But that's a whole other thread, and probably better in a non-DIR forum.

I don't dispute the advantages of helium deeper than 130' or even 120'. And I'm not disputing the advantages of helium in the 100-120' range, just trying to figure out what they are.


Personally, I think the dives I do in that range are in pretty good conditions. The water is 68-72 degrees. The visibility is at least 30', usually closer to 100' or more. There's minimal current. And no boats ! Okay, so there's 100' of rock between me and air. :14:

I think my Fundies instructor's story shows that you can think you can handle anything, but when it actually happens, you may find out you can't. The most chilling thing about that story, to me, was the fact that he had no idea at the time that he was so narced he was turning a valve the wrong way.

And a few times when I realized I was narced it was after the dive was over and I was going over it. But I can also say that I felt more narced during a mix dive in the 150s range and actually knew it during the dive. However, it was much more apparent after the dive. I don't know how I would have felt if I was breathing straight air. Although I don't think it would have been much different. I did a dive to 140 on air and felt the narcosis there too, maybe a little more narced, but the conditions were also not as good as during the 150 range dive. Another dive in the high 130s wasn't as bad as the 140 dive. I don't know if it was better conditions on the 130 dive, more experience, or a difference of 4' in depth.

 

[Thalassamania]

With respect to oxygen: Most of the folks I know who did an oxygen tollerance test will tell you that at sixty feet in the chamber they felt a little buzz, went on oxygen and the buzz went away, and it came back when they went off oxygen. Not conclusive, and at an endpoint, but still?

 

[grazie42]

As with a lot of the "science" of diving there is no black and white answer (?)

There is a chance that oxygen is narcotic and a chance that it isn´t. Evaluate the consequences of both possibilities, find your "truth" and consider the risk of being wrong. Then choose your method of calculating narcotic depth and go dive it. Chances are you won´t ever find out if you are right or wrong.

The fact that no-one can call you wrong and prove it is one of the things that makes decompression and most of the other stuff interesting to talk about and since we won´t all ever agree we can keep discussing it endlessly...