Deep Air Dives In Tech Classes

[Billy Northrup]

Sometimes in the confines of a class air gets you into deco quicker then work your skills on the accent and get back on the boat. The boat probably has recreational divers on it you can borrow some surface interval time from before on to the next dive site

Add: I dive the same dive like groundhog day all week. On air at almost precisely 90ft my hearing changes and I can feel a "sensation". I can vary between 80 and 100 and it goes on and off like a light switch. Thirty two percent buys me about 20-30 feet, it's much less pronounced. I've never grown a tolerance for being narc'ed, I just know I am and compensate accordingly.

I have a romantic love affair with Helitrox, that's another story

 

[victorzamora]

So the dives up to that point it was mandatory to do on air?

Not to answer for Kate, but: Yes. Tec50 is not a trimix course, and, as such, the diving is done on air/nitrox.

 

[rjack321]

Over heard some discussion among some tech students about some of their deeper dives being on air and being narc'ed. Is there are purpose to doing such dives? Do most tech classes have this as a component? I know a few agency's do not but was just wondering why add a possible issue to a tech class. Not really asking if you agree or disagree just looking for some explanation if there is any.

Thanks,

Years ago the explanation was that you had to "learn to adapt" to narcosis. The concept of adaptation has been proved to be false now (kevrumbo posted the citation).

The same courses are now taught with the explanation that helium is too expensive or not available. Although that doesn't really explain why you would take a deep air class where helium actually is available and fairly inexpensive - like Florida.

So the purpose/role of those courses has changed over time. And they are offered places where they don't need to be offered. If nothing else, they are highly effective chest thumping exercises.

 

[Dan_P]

I think maybe the reason for some deep air dives, is simply that gas density wasn't identified as a problem to be solved by way of adding helium when most courses were created and most agencies formed - the below reference is as recent as 2016.
In fact, using gases other than air was extremely controversial even relatively recently - I believe it was in 1993 that nitrox was banned at DEMA, however briefly.

[EDIT: The point about Nitrox at DEMA is to illustrate recency of controversy - NOT to give the impression that nitrox is a suitable gas choice when the depth is too great for air!]

A guess on my part is that a change in such matters may be slowed down significantly due to fear of legal liability, on part of organizations.
(e.g. if an organization changes position on deep air, could relatives of previously injured divers who followed past procedure, litigate said organization?)
If so, this would naturally be particularly relevant to organizations who don't have insurance.
(most of the mainstream ones still aren't underwritten by any insurance broker, to the best of my knowledge)

If that's the reason, my personal opinion is that's extremely unfair to diving organizations and divers alike, but that'll be a side note on my own accord.


For an extensive yet approachable elaboration on the subject of gas density and how it impacts us when diving, I'll refer to the very helpful work published by @Dr Simon Mitchell in Rebreathers and Scientific Diving Proceedings 2016.
The section from page 66 onwards may very well be of particular interest.[1]
The setting of this was focused on rebreather diving, but the human physiology is of course identical across rebreathers and open cirquit.

I take note of this paragraph in particular;
"For the purposes of planning rebreather dives and in the current absence of more definitive or contradictory data, it seems prudent to recommend an ideal maximum gas density of 5.2 g·L-1 (equivalent to air diving at 31 m [102 ft]) and an absolute maximum of 6.2 g·L-1 (equivalent to air diving at 39 m [128 ft])."

[1] Respiratory Physiology of Rebreather Diving. Gavin Anthony, Simon J. Mitchell. Rebreathers and Scientific Diving. Proceedings of NPS/NOAA/DAN/AAUS June 16-19, 2015 Workshop

 

[Compressor]

Here in Libya due to several reasons, economics and availability of expertise, MANY local divers dive to 50 - 60 meters on air and do spearfishing. I know some that do it at night. They decompress on 100% O2 and survive to talk about it. They do it frequently. He is incredibly expensive and out of reach for most divers and/or unavailable.

The 50 - 60 meter diving is done on a recreational rig withOUT redundancy

This is interesting to me. Can you tell us the typical tanks used and the times spent at depth and @ deco stop. Thanks.

 

[Diver0001]

Deep air is absolutely stupid. The only reason to dive deep air is because you don’t have enough money to do the dive in the first place.

I guess it depends on what turns your crank. I still make a fair number of dives with incursions >40m up to about 50m or a little deeper on air. They're pretty trivial dives in terms of the work involved but I actually choose for that. I'm trimix trained but I don't do drugs or drink and the narc is, I will admit, kind of the goal of some of those dives.

That said, it's unpredictable. Sometimes I'm fine at 50m and sometimes I'm pretty bonked at 36m. There's no telling how you'll feel until you get there so we always account for turning the dive early.

I've done many hundreds of such dives over the years. I'm not going to suggest that it's for everyone but just blanketly stating that it's stupid unless you are poor is kind of insulting to anyone who chooses for it and to anyone who is poor.

R..

 

[BoltSnap]

This is interesting to me. Can you tell us the typical tanks used and the times spent at depth and @ deco stop. Thanks.

First, please note in regards to this practice, I never do it myself or teach or tell anyone to do it. In fact, I "preach" against it every opportunity I get. I am just relaying what's going on here and what I have to deal with in Libya.

Typical tanks (always) are steel 18L 220B with "Yoke" connection. They "may" have a "Y" valve and the divers "may" use one regulator on each valve post (big "may have"). I am not sure of the times for dive time and deco stops since they vary, but they are based on different tables that are passed on by different sources. People may have information from French navy tables, others use CMAS and US navy. Their knowledge is very superficial and is based on "rumor" and "hand me down" sources. There is a very high disproportionate rate of dive injuries and fatalities in Libya and many divers were injured several times in their diving career. Few months ago one commercial diver died in the chamber (there is only 1 - 2 chambers in Libya and typically not available for sport divers) after making 3 repetitive dives in one day to circa 50 meters on air spearfishing. There are many who are doing it without obvious injuries. It is also interesting to note that the 100% O2 bottles they use aren't "O2 clean" at all I haven't heard of a Tank exploding yet however (again, I am not stating that it is OK to do this or that I do it but I am just reporting what's going on here).

In Libya, they are challenging all of the safe diving rules

 

[stretchthepenn]

Deep air is absolutely stupid. The only reason to dive deep air is because you don’t have enough money to do the dive in the first place.

Please don't bring in the "if you can't afford to ______, you have no business ______" argument. There are many valid arguments to be made, but elitism isn't one of them.

 

[RainPilot]

Please don't bring in the "if you can't afford to ______, you have no business ______" argument. There are many valid arguments to be made, but elitism isn't one of them.

I don’t believe AJ is being elitist. I believe it’s along the lines of seeing someone racing motorcycles in a T shirt and shorts, no helmet and finding out it’s because they can’t afford protective clothing.

We may admire their derring do and pluck but they are still being very unsafe.

If someone said “If you can’t afford cave training then you shouldn’t dive caves” would we disagree?

 

[stretchthepenn]

I don’t believe AJ is being elitist. I believe it’s along the lines of seeing someone racing motorcycles in a T shirt and shorts, no helmet and finding out it’s because they can’t afford protective clothing.

We may admire their derring do and pluck but they are still being very unsafe.

If someone said “If you can’t afford cave training then you shouldn’t dive caves” would we disagree?

I see your point, but I mostly disagree. The greater point is that financial resources do matter, but telling someone "you're too poor to ______" is, at its core, elitist.

Certainly, if someone is doing something blatantly unsafe--such as racing motorcycles without any safety gear whatsoever or, as you pointed out, cave diving without training--then it's ethically correct to step in and say "dude...don't do that."

However, what we're discussing here doesn't push those extremes. Let's say that our motorcycle racer has secondhand riding gear, or a previous-generation crash helmet. Modern protective clothing would make our hypothetical motorcyclist much safer, but unless we're discussing elite racing or particularly dangerous stunt riding, then older gear will be entirely adequate, and telling the rider to come back when he's rich enough to afford top-of-the-line equipment is neither necessary nor desirable.

With the analogy of cave diving, there's a big difference between saying, "you really should get cave training before attempting that dive" and saying, "you can't afford cave training, so go away."

I'm sensitive on this subject because, back when I was a relatively new diver and working as a retail-wage-slave, I was a member of a scuba club that held its meetings over dinner, at a spaghetti restaurant that charged us a modest ten bucks or so per head. One member floated the idea of changing the meeting site to another restaurant, one that was much more expensive, and I ventured the opinion that changing venues wasn't the best idea because some of us (such as myself) were on budgets. The member came back with "Well, if you can't afford this, why are you even diving?"