An age-old question: ways to 60m.

[Dr Simon Mitchell]

Without the diver's workload, this article is very incomplete.
I can't find this extremely important value, but perhaps someone can ?

Yes, you are right. Can't believe we did not notice that. The workloads are described in another workshop proceedings that is referenced in our article. Here is a figure from that paper:

Each graph (showing end tidal CO2 against time) is a single test dive with a different rebreather in each test - both with nitrox at 40m I think, so gas density up around 6g/L. You can see that in the top panel, when the diver exercises at 100W and 125W (duration of exercise corresponding to the magenta bars) the end tidal CO2 (blue line) peaks up over 8.5 kPa (a dangerous level). Each time he rests (between the magenta bars) the CO2 falls again. However, in the bottom panel, even exercise at 125W does not cause a dangerous increase in end tidal CO2. This reflects a difference in design / work of breathing between the two rebreathers.

Anyway, to answer your question, Gavin's work was based on a graduated exercise regimen peaking at 125W. Its not particularly heavy exercise, so highly relevant to normal diving. Normal finning at ~0.5-1 knot is probably somewhere around 100W.

These diagrams come from
Anthony TG, Diving re-breathing apparatus testing and standards UK/EU perspective. In: Vann RD, Mitchell SJ, Denoble PJ, Anthony TG, eds. Technical Diving Conference Proceedings. Durham, NC: Divers Alert Network; 2009, pg. 218-36.

The workshop proceedings can be downloaded for free from the DAN library

https://apps.dan.org/publication-library/

Simon M

 

[Blackcrusader]

Please explain the workload reduction procedures for dealing with emergencies: burst disk failure, hose ruptures, and other equipment failures. Dive buddy emergency like loss of consciousness or oxto convulsions.

Edit: now just to be clear, the complexity diving at the same depth varies on conditions. Surely we can all agree that diving inside a real wreck (not an artificial reef) in cold water is not the same as a tropical dive in the blue with no overhead.

I'm happy diving 30m - 45m on air. I eally do not want to go any deeper and I will not enter wrecks. I dive in open water with temps from 22c to 30c but mostly in the 25c - 28c range in Tshirt and Shorts.

In May in the Maldives on one shark dive I went to 44m depth. My buddy I see was deeper. I used my torch to signal to him to ascend so we could not be so deep for too long. AL80 21% so need to be able to clear deco. Dang he went to 55m. I was not pleased because if he had an issue not sure what I would have done. We both cleared out deco obligations and was on the surface after 42 minutes with plenty of gas.

Another thing, I have learned not to over exert myself and will call a dive. I've seen some divers struggle to fin up from 40m in currents. Not me, I revert to what BSAC training gave me which is a CBL. Controlled Buoyancy Lift. Why should I exert myself when I have a very good lift device that can bring me up to shallower depths and I can maintain my nice slow unstressed breathing. Other PADI divers have told me they have never heard of a CBL or been trained that way. One PADI instructor told me it was not a PADI standard... I replied well maybe it should be.

I was with a diver whose inflator hose assembly blew out of his BCD at 35m depth. He struggled to maintain even 35m depth. I swam to him attached my DSMB to his BCD Ring and gave him a controlled ascent to the surface at 5m a minute. At the surface the fully inflated DSMB was laid horizontal so he could rest on it and wait for the boat. He did not need to fin just took that nice slow elevator ride with no sense of panic or exertion. He did not have an SMB but bought one before his next dive.

I reallly don't like to over exert myself on dives. There are some washing machine dives done with sharks in Fuvamulah Island where you need to work hard for a whole dive.

 

[scubaozy]

and CCR where is well forgotten old good SCR... (Some Draeger units still exists on market) Some sort of compromise between OC helium prices and complexity of CCR.

Dräger is not an exactly an option for 60m. It is a constant flow device that is adjusted with using one of the standard 32/36/40 percent orifices. If you used 32 percent orifice along with ean32 tank, you will have roughly 28% o2 in the loop depending on work load and depth. Your mod would be 40m at 1.4.

 

[Kay Dee]

Since this research was published in 2016, older training programs won't mention it.

Well, thats certainly not right, the training programs definitely should not only mention it, but have make the prospective student read before signing up. Then at least the student knows (some of the risks) and can make a somewhat informed choice whether to still proceed. So, very very remiss of those agencies, and certainly doesn't show they have much faith in their training programs.

Training agencies underestimated the risks of deep air diving, and overestimated the possibility of adaptation, too.

Thank you for posting the direct links. You would think that these studies after peer review would end arguments. But then some people think the earth is flat even though the ancient Greeks figured out the circumference of the earth thousands of years ago. I guess news travels really slowly in places. So I should accept that this debate will still be going on in 4500 AD

No one said it was for everyone, nor that anyone should do it. Just that is does get done in some / many circumstances. Is there some risk involved, yes, but there is risk in a lot of 'sports'. So while one can't eliminate the risk, one needs to first know there is a risk, accept it (or not) and then do one's best to manage that risk (in numerous ways). Or not accept it at all and stay out of the water (if one is so anti-air / dependent on mixed gas to take that 'risk').

A case in point of when that decision might need to be made. I was involved in the discovery of and first dives on a famous but relatively remote WWII wreck. At the time we were taking the dive vessel back to Singapore from Bali, no one else on board ‘cept me, the skipper and his wife, and the skippers best friend. And there was no helium left on board as the last lot of OC’ers had used it all (but there was still enough o2 for deco). The wreck lays in 62m / 200ft. I don’t need to say what I or the others did (there was no question about that), but I wonder what the ‘no deep air folks’ would have done in that circumstance, as there was no ‘coming back out tomorrow’ to dive it. As matter of fact it was not dived again until we went back out the next year with gas on board (and my CCR this time) some 14 months later.

This doesn't mean that you could overcome physiology by taking a class that somebody created 20 years ago. It just means that their training program is outdated.

Then I am very glad I availed myself of that training back in the very early 90's before it became outdated, otherwise I would have spent an awful lot of time sitting on the beach or a boat!

 

[Nick_Radov]

In May in the Maldives on one shark dive I went to 44m depth. My buddy I see was deeper. I used my torch to signal to him to ascend so we could not be so deep for too long. AL80 21% so need to be able to clear deco. Dang he went to 55m. I was not pleased because if he had an issue not sure what I would have done. We both cleared out deco obligations and was on the surface after 42 minutes with plenty of gas.

Regardless of gas selection, it's stupid to use a single tank go to that depth or incur a deco obligation — especially if your buddy is so incompetent that he just leaves you behind. I know lots of divers do it and usually nothing bad happens but you're one equipment failure away from having a really bad day. More skilled and experienced divers prefer to stack the deck in their favor so that no single failure can cause a serious problem and they always have multiple options on how to manage it.

 

[Kay Dee]

Edit: now just to be clear, the complexity diving at the same depth varies on conditions. Surely we can all agree that diving inside a real wreck (not an artificial reef) in cold water is not the same as a tropical dive in the blue with no overhead.

I totally agree, and I would expect anyone with any sense would to. And that's why I say "one size does not fit all'.

 

[David Carron]

Regardless of gas selection, it's stupid to use a single tank go to that depth or incur a deco obligation — especially if your buddy is so incompetent that he just leaves you behind.

I don't think there's any debate: air dives in the 50m-60m range on a single tank and without any accelerated deco procedures are more dangerous than with, more dangerous than with gas redundancy, and more dangerous than with a lighter, less narcotic gas.

The debate, such as it is, seems to be more centered around how much more dangerous.

The significant numbers of dives like this on sites such as the Togo (55m, and I'm guessing maybe ten per day during the summer months) may indicate that adjectives such as "stupid" are perhaps an overestimation.

 

[leadduck]

In May in the Maldives on one shark dive I went to 44m depth. My buddy I see was deeper. I used my torch to signal to him to ascend so we could not be so deep for too long. AL80 21% so need to be able to clear deco. Dang he went to 55m. I was not pleased because if he had an issue not sure what I would have done. We both cleared out deco obligations and was on the surface after 42 minutes with plenty of gas.

So did your buddy explain why he left you to go to 55m alone with a small tank of air; was that the plan you had discussed before the dive?
It's a usual story of nitrogen narcosis: divers forgetting to check their depth and SPG, not noticing that they're far deeper than their buddy, forgetting the dive plan, but afterwards pretending that they didn't feel impaired at all, just were a little distracted, but totally fine, and wasn't it a nice dive, no problem.

 

[Celt]

Well, thats certainly not right, the training programs definitely should not only mention it, but have make the prospective student read before signing up. Then at least the student knows (some of the risks) and can make a somewhat informed choice whether to still proceed. So, very very remiss of those agencies, and certainly doesn't show they have much faith in their training programs.

No one said it was for everyone, nor that anyone should do it. Just that is does get done in some / many circumstances. Is there some risk involved, yes, but there is risk in a lot of 'sports'. So while one can't eliminate the risk, one needs to first know there is a risk, accept it (or not) and then do one's best to manage that risk (in numerous ways). Or not accept it at all and stay out of the water (if one is so anti-air / dependent on mixed gas to take that 'risk').

A case in point of when that decision might need to be made. I was involved in the discovery of and first dives on a famous but relatively remote WWII wreck. At the time we were taking the dive vessel back to Singapore from Bali, no one else on board ‘cept me, the skipper and his wife, and the skippers best friend. And there was no helium left on board as the last lot of OC’ers had used it all (but there was still enough o2 for deco). The wreck lays in 62m / 200ft. I don’t need to say what I or the others did (there was no question about that), but I wonder what the ‘no deep air folks’ would have done in that circumstance, as there was no ‘coming back out tomorrow’ to dive it. As matter of fact it was not dived again until we went back out the next year with gas on board (and my CCR this time) some 14 months later.

Then I am very glad I availed myself of that training back in the very early 90's before it became outdated, otherwise I would have spent an awful lot of time sitting on the beach or a boat!

The excitement, pleasure and satisfaction of diving an unknown wreck or reef for the first time can’t be measured by science, and it’s hard to explain the motivation behind a person wanting and willing to go there, I’ve learned I could have made dives more safely and efficiently but don’t regret making them.

 

[Blackcrusader]

So did your buddy explain why he left you to go to 55m alone with a small tank of air; was that the plan you had discussed before the dive?
It's a usual story of nitrogen narcosis: divers forgetting to check their depth and SPG, not noticing that they're far deeper than their buddy, forgetting the dive plan, but afterwards pretending that they didn't feel impaired at all, just were a little distracted, but totally fine, and wasn't it a nice dive, no problem.

Yeah we discussed it after the dive on the boat. I've dived with him hundreds of times. He's not an instabuddy. It was not a case of narcosis or checking his spg which he had done, he was getting a video of a shark and headed deeper. As this was at the early part of the dive he had plenty of gas and we ended up having a nice dive.