An age-old question: ways to 60m.

[leadduck]

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.

While I used to ridicule GUE (before the science caught up with them) for switching to trimix at 30 meters, I have since learned that their configuration and philosophy is based on how to return safely after a serious emergency occurs.

While I don't dive their configuration, I try to adopt their philosophy of how do I and my buddies get out alive when something serious happens. Keeping gas density at 5.2 g/L gives some room with increased gas density caused by increased CO2 generation.

Maybe I'm too paranoid from when Andy Grove ran Intel (he wrote Only the Paranoid Survive). But I have a little girl I hope to walk down the aisle one day.

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.

If you disagree, please click on disagree so I can add you to my ignore list.

Regarding GUE, I think it's because their training program was initially all about cave diving. In open water, you can mitigate the risk of nitrogen narcosis by ascending as soon as you feel it coming. Not very reliable in practice, but at least there's a chance. Far inside a cave or a big wreck: no chance. Plus the usual risks of overhead diving; getting one narced diver out of a cave would be quite a challenge for the team. So avoiding air even at 40m far in the overhead environments is not as overly cautious as it seems to open water divers.

 

[Blackcrusader]

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.

Yup you have written so many times that deeper than 30m must be on Helium. We get it. Not available.
He was slightly below me but not far away in distance. I could have joined him but meh, decided not to. In any case we are always solo divers even when with a buddy. We were not alone there were other divers with us. Thanks for your concern.

Would you ever dive with no Helium avaible Nitrox 27% to 35m - 40m with a 40% nitrox tank mix for staged deco?

 

[Nick_Radov]

Regarding GUE, I think it's because their training program was initially all about cave diving.

GUE had training courses for ocean diving from the start. Jarrod Jablonski founded GUE partly because the idiots running some other "technical" training agencies thought that taking students to 190 ft / 57 m was an acceptable practice.

https://indepthmag.com/twenty-five-years-of-gue/

 

[Nick_Radov]

Would you ever dive with no Helium avaible Nitrox 27% to 35m - 40m with a 40% nitrox tank mix for staged deco?

I'm not going to waste time answering silly hypothetical questions. Helium is always "available" if you plan far enough ahead and pay what it costs.

Regardless of back gas selection, I wouldn't do a planned deco dive on a single bottom gas tank. Or with a teammate who would disregard the dive plan and abandon me to chase a photo op.

Nitrox 40 is an odd and mostly useless deco mix, at least for typical ocean diving square profiles. Too rich to significantly reduce your bottom gas minimum pressure, too lean to significantly accelerate deco during the shallow stops. So I have no idea where you came up with that.

 

[SelfDiver]

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:

View attachment 907567
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

Not really on topic but while you are here...

Is there a theoretical way to train for higher gas densities similar to what climbers do for high altitude training? Is there some sort of Sherpa physiology equivalent for higher gas densities?
How about narcosis? Can the effect of high partial pressure Nitrogen on the nervous system be mitigated with training/drugs/pysiology?

 

[BoltSnap]

In open water, you can mitigate the risk of nitrogen narcosis by ascending as soon as you feel it coming.

Yeah, right. You are most likely not going to know about it or discern that you are under the influence.

 

[iho]

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.

Some play around Drager... Who can stop you attach hoses to 2 valves and get 24 l/m 23/45 ... Just remember not only maximum operating depth but minimum too. But you Gona have deco in any case so you are not gonna use Drager shallower 21m on ascent... This is theory only though

 

[Kay Dee]

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.

You may have missed my point. I just used that specific instance only as an example so to speak. We had been out for over two weeks doing air dives to those depths or thereabouts on wrecks almost every day (when I said we were 'delivering' the boat from Bali to Singa's I didn't say we went straight there.) I just used that particular dive example to ask what all the 'never deep air' chaps would do in that situation. That wasn't a 'one off' occurrence for me, although that particular wreck we had been looking for for five long years.

 

[Kay Dee]

I Helium is always "available" if you plan far enough ahead and pay what it costs.

Always? I'm calling BS on that!

Obviously is in the USA or some such place, but………………...first time I went to Bikini (before it opened to the public) to tech train the operators their, there was no helium there, nor available in the region at the time, nor any option to 'plan far enough ahead' given their training schedule and their opening schedule. Sure, granted that was back in the day, but is used just as an example of certain situations vis a vis you "always available". Another is an example I give in another post their are still situations much more recently, and still today, where there is simply no helium available in certain locations / time frame. Restrict yourself all you like, that's your prerogative, but that doesn't mean others have to, or should do, if or when a situation arises. Besides, a lot of the decision making - if you could call it that - around condcuting said air dives should hinge upon informed, repeat informed, risk tolerance / acceptance.

 

[wetb4igetinthewater]

Helium is always "available" if you plan far enough ahead and pay what it costs.

One of my motivations for CCR is the lack of availability of helium in Greece. To support deep archaeological expeditions is a logistics nightmare.

Sure you can find a few dive centers that carry helium. One in the Ionian Islands. One on Crete. One in the Dodanese. Not great coverage for 2000 islands.

This reminds me of the guy here on SB who says you can get twinsets anywhere if you plan ahead and there is zero reason to dive side mount in open water. Divers limit themselves with this belief.