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Inhale-pause-exhale also takes more effort on your breathing muscles (most time under tension, rarely relaxed), producing more CO2 again. Shouldn't the pause state better be relaxed, not fully inhaled, neither fully exhaled to the residual volume? ( The Process of Breathing | Anatomy and...

In OC this can be a continuum, depending on how you pick your mix vs depth. If you stick to standard gases only, then a rule like "EAN32 until 30m, 21/35 for 30-45m" makes a 35m dive very expensive. There's a big price step from air or EAN32 to 21/35, and no surprise that people want to avoid...

From a 2012 interview with George Bass in discovermagazine: At Yassi Ada, one of our most skilled, experienced divers, Eric Ryan, was very near death when we pulled him from the water with an embolism. And then we had a sponge diver also brought to us with the bends, or decompression sickness...

Theoretically, yes: a risk has multiple factors that you can trade off against each other. The challenge with "assess and evaluate the risk" is, that this is not about your gut feeling and limited personal experience, but about hard data. Avalanche risk in alpine ski touring is a good example...

Exactly. And I think that's the biggest risk of deep air: that on some occasion, maybe after 200 uneventful deep air dives, something unexpected happens (reg freeze, getting stuck, dry suit leak, buddy has an issue and needs help, whatever) that causes workload and stress, your SAC rate goes up...

"That's a very plausible observation and not a contradiction." meant that your observation that you often heard divers complain about overbreathing their regs and not getting enough air at depth, does not contradict the idea that the problem is caused by internal airways resistance in their...

Position of tank is also influenced by shoulder straps, maybe they are all too loose and your tank hangs too low. After descending, in horizontal position, move your tank a little further up and tighten the shoulder straps and belt.

The yankees dive so cautiously because their healthcare costs so much. No free chamber rides, can you imagine?

That's a very plausible observation and not a contradiction. High airway resistance in the lungs *feels* like the reg is hard to breathe. Same like immersion pulmonary oedema (IPO): diver signals out of gas and switches regulators, but the new reg isn't better because the problem is actually...

The issue with gas density in deep air has nothing to do with overbreathing the regs. It's about the internal airway resistance within your lungs. At 60m, your lungs cannot achieve the same maximum SAC rate with air as with trimix, or with air at 30m. If high workload happens (planned or...

When people denounce deep air diving today more than 25 years ago, I don't think it's because people got more risk averse. It's rather that back then we didn't know better, had a few misconceptions about adaptation to nitrogen narcosis. But we know more about it today, and we have more accident...

If you'll be back a year later with a CCR anyway, sure, why not skip a 62m dive on air? Think about the many beautiful wrecks you still want to see, and that one serious accident will end your diving career. Particularly if you love wreck diving and want to continue doing it a lot, you would...

You missed my next sentence: "Not very reliable in practice, but at least there's a chance." I think if you're narced, your buddies will notice it before you do. When your brain slows down, how will it notice that it got slower, that your response time got longer, your situational awareness is...

That doesn't contradict what I wrote; the origins of GUE lie in the WKPP, and many of their standards and procedures are obviously aimed at safe cave diving in teams (and then spawn criticism by people who find them unnecessary in open water ocean dives). Deep air for example is more dangerous...

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...

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 thing with hypercapnia due to workload while breathing gas with high density is described here: https://dan.org/alert-diver/article/performance-under-pressure Full paper: https://www.omao.noaa.gov/sites/default/files/documents/Rebreathers and Scientific Diving Proceedings 2016.pdf page...

I have a very tight 7mm and found it easiest to jump from the boat with the wetsuit in my hand, don it in the water, then climb back on the boat to close the zipper.

Oh, respect is what you desire? Let's recall a few things about your "heroes": "The Rouses were considered a formidable diving team, but their overconfident and ego-driven attitudes sometimes led them into risky situations. They lacked experience in deep wrecks and were relatively...

Nitrogen "narcosis" doesn't mean you're unconscious, that happens only in extreme cases. It usually means you're mentally slow, sleepy, confused with delayed response, dizzy. Symptoms also include being euphoric, over-confident, making bad decisions; some hallucinate. The Rouses were obviously...