Deep Air Question

[Rick Murchison]

I don't think anyone here will dispute the physiological or safety advantages of trimix over air for dives over 100' or so. Trimix is clearly safer in every way.
But... when looking at diving the site or not, with air the only gas available, the go/no-go depth suddenly deepens. It's a matter of acceptable risk. I would never urge anyone to accompany me on air below 110', they'd have to ask. But as FredT has so eloquently explained in an earlier thread, there are ways to reduce the risk to an acceptable level. Planning, training, training and planning. And planning.
Rick

 

[Ontario Diver]

WreckWriter once bubbled...
I have no idea what's involved in a deep air class.

The IANTD or TDI Deep Air Class is more about deco diving beyond the NDL time limits not as much as the depth limits. But they do cover the O2 Tox and Narcosis in detail. There was definately a flavour of "More Time = Deco & More Depth = Trimix" on the course.

 

[WreckWriter]

Rick Murchison once bubbled...
But... when looking at diving the site or not, with air the only gas available, the go/no-go depth suddenly deepens.

Bikini is a perfect example. Spectacular wrecks but only air. Would you go? I sure would....

Tom

 

[Spectre]

tombiowami once bubbled...
Would any deep air students out there dive to say 30' and then switch to a tank that contains nitrous oxide?

If not, why would you go to 150' and do it?

Nitrous oxide is not the same as air at elevated partial pressures. It's a chemical compound N2O. It's _much_ different then air [79% N, 21% O2 in the case of 'hyper' air].

Nitrogen is an inert gas in your respiratory system. You can't breathe water [H2O], so what makes you think you can breathe N20?

The problems with breathing nitrous is that you have to 'cut' it with O2... if you take a 50% breath of N20, then 50% breath of air, you're getting 10.5% 02, which is hypoxic.

And even if you created a mix with N2O and O2 to enable breathing, what about decompression...

 

[MikeFerrara]

Hey all,

With respect to something I said in my last post...

A really good driver may outdrive a bad driver even when under the influence. When deciding what impairment can be tolorated maybe you need to take the baseline into consideration.

My intention was not to condone or encourage driving drunk or diving narced. We should be sharp and at our best when we dive and for that matter when we drive. The point I was trying to make is that we should not be so quick to judge others because they have set different limits for themself than we have for ourselves. Hope nobody misunderstood.

 

[noshow]

if you are DRUNK you are DRUNK... if you are NARCED you are NARCED...

So the trucker who spends his life on the road driving is ok to drive DRUNK and is less likely to kill someone than the rookie DRUNK driver? "I'm only a little drunk but I won't kill someone tonight, I promise, I'm ok." They ususlly get home but their chances are drasticlaly reduced. Why not cut out the problem and take a cab? A bit of an inconvenience and greater expense but if you want to drink and get home safe, why not?

So the diver who spends his life diving as an instructor is ok to dive NARCED and is less likely to kill someone than the rookie NARCED diver? "I'm only a little NARCED but I won't kill someone this dive. I promise, I'll be ok". They usually get home but their chances are drastically reduced. A bit of an inconvenience and greater expense but if you want to dive deep and get home safe, why not?

It's too simple...

 

[MikeFerrara]

I sure do regret the analogy I used.

This is an issue that I think everyone oversimplifies. As I said no impairment is better than some impairment. However, there are other sources of impairment both phisical and mental. Many things effect our ability to perform at any given time. Maybe at some depths there are factors that may effect an individuals performance to a greater degree than narcosis. Narcosis seems to get all the attention though.

 

[WreckWriter]

noshow once bubbled...
if you are DRUNK you are DRUNK... if you are NARCED you are NARCED...

That's obviously a major oversimplification. Sure, if you are..., you are..., but, using the drunk analogy again, don't you think that the guy who had 3 beers is maybe not quite as dangerous as the guy who had 30? Same trick for narcosis, you're not as narced at 130 as you are at 230.

Impared yes, but there certainly are degrees of impairment. That's why you mix based on PO2 and END.

Tom

 

[MikeFerrara]

I am not in favor of deep air. I am also not in favor of a diver who thinks he is ok at 95 ft but thinks the next guy is dangerous at 105.

 

[JamesK]

Mike,

Just interested in where you draw the line on deep air. Your statement of 95 compared to 105 feet sounds like a statement made by someone who I was talking to about it. My personal limit is 120 on air. Deeper only in an emergency. When I told this to someone else, they basically made the same statement, well why not 130 or 140 or 150? Well then if not 150 why not 160? My question was "Where does it stop?" I was just wondering what you considered too deep for air. If you already mentioned this, sorry.