recreational trimix

[MikeFerrara]

MechDiver once bubbled...


Is there an agency that gives trimix cert without dives??? Or do you mean EAN?

Phil

For the time being I am refering EAN hower someone will come up with a no-dive trimix class eventually.

Ascent rate is always critical and divers should be tought to control it and be evaluated and (if needed) receive remedial training in all classes.

An instructor can't eveluate diving skills without being in the water so a non-diving EANx (or other) card means nothing to me.

OK... there are other card that don't mean anything to me too.

 

[Genesis]

the LEVEL of control necessary for a He-based mix is higher than that for an N2-based mix, correct?

Is there not a difference in the level of skill that is a "safe minimum" for the two mixes?

 

[WreckWriter]

I'm still not buying that there's a major difference.

 

[MikeFerrara]

I have heard that ascent speed and holding ones stop depth is more critical with He but I don't know how much of a factor it really is though especially within the "NDL" or "minimum " decompression. It seems to me that if we give up the concept of working to minimums and teach/learn good technique at all levels there wouldn't be a big difference in skill requirements.

Someone like BRW or Dr. Deco might be able to tell us if He would actually form bubbles faster. I think there may be more to it than just how fast the gas comes out of solution. I have also heard that He bends are worse than Nitrogen bends. I havent worked up the nerve to test it though.

 

[MechDiver]

MikeFerrara once bubbled...
I have heard that ascent speed and holding ones stop depth is more critical with

Is that not what the RGBM tables/software is based on? When we went to RGBM table based profiles, the ascent speed from depth (>160) was 10 fpm vs 30 using VPlanner. And we held that speed through the entire deco profile.

It's my understanding He creates smaller bubbles that offgas faster and deeper, making deep slow ascents and spot on deco stops much more important than non-mix profiles. That is training issues aside.

Also very interested in Dr. Deco's comments.

Phil

 

[WreckWriter]

MikeFerrara once bubbled...
I have also heard that He bends are worse than Nitrogen bends. I havent worked up the nerve to test it though.

I've also heard, and seen some evidence of it, that helium hits are worse. Perhaps this is part of the reasoning behind thinking that the asdcent rate might be more critical, in that it's a heck of a lot worse of you do get bubbles.

Tom

 

[nradov]

I've seen a lot of bad information posted in this thread so let me see if I can clear up a few misconceptions. Certainly it is always important to do the proper ascent, but for relatively short and shallow dives the presence of whatever percentage helium makes no difference. In other words, the ascent from a dive to 80ft for 40 minutes on 30/30 trimix should look the same as with 30% nitrox. Part of the confusion here has arisen from divers looking at flawed tables and decompression programs based on the Buhlmann model. They seem to tell you that trimix requires longer and deeper deco than nitrox. But in reality the ascent profile it gives you for trimix is closer to correct, and the nitrox profile is often less deco than would be optimal for minimizing damage. Keep in mind that no profile you get straight out of a deco program will really be correct, it's just a rough starting point.

If for some reason you do end up going straight to the surface without stopping at all the helium doesn't increase the risk of getting bent, or cause worse DCS symptoms than nitrogen. This is just more nonsense spread by those who don't understand deco, and has no reliable evidence to back it up.

In summary, breathing helium does not make any aspect of diving more dangerous.

The hilarious thing is that Max Nohl was diving with helium back in the 1937, yet here it is 2003 and most divers still see it as some huge scary mystery. You can thank the dive industry for that one.

-Nick

 

[MechDiver]

nradov once bubbled...
I've seen a lot of bad information posted in this thread so let me see if I can clear up a few misconceptions. snip

If for some reason you do end up going straight to the surface without stopping at all the helium doesn't increase the risk of getting bent snip

In summary, breathing helium does not make any aspect of diving more dangerous.

Sorry, but everything you said in this post is contrary to everything I have been taught or read concerning trimix diving and deco. What you say "may" be accurate, but I need alot more evidence of that fact that your opinion. If you can backup your statements with fact...?

Phil

 

[newton]

MechDiver once bubbled...


As I would expect them to be Tom. I was thinking more about West Bumscrew, Montana

Hey, I live there!

In any case, getting Nitrox is a problem here, let alone mix. However, over in Montana most places have never even here of *any* dive agencies aside from the big-3 (PADI, NAUI, SSI). I suspect TDI, IANTD, and GUE cards would all be looked at with suspicion. But, the upside is there isn't any need for deep diving. The water is way too murky by the time you get that deep, so why bother when there's really not that much to see except the bottom of a lake anyway?



Nate

 

[MechDiver]

newton once bubbled...


Hey, I live there!

In any case, getting Nitrox is a problem here, let alone mix. However, over in Montana most places have never even here of *any* dive agencies aside from the big-3 (PADI, NAUI, SSI). I suspect TDI, IANTD, and GUE cards would all be looked at with suspicion. But, the upside is there isn't any need for deep diving. The water is way too murky by the time you get that deep, so why bother when there's really not that much to see except the bottom of a lake anyway?

Nate

Yes, but with mix you can see and remember the murk so much better

Phil