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Watch your breathing pattern. Do not stay inhaled for longer time, instead rest exhaled. Some divers who stay inhaled for a longer time can compensate trim by moving weight higher up (not good but works), but in your case with little weight, no such workaround.

Note that the publication (Mitchell: Respiratory Physiology of Rebreather Diving) shows experimental results where between 6g/l and 7g/l half of test dives couldn't be finished. But these were working dives and I don't see the parameters (how much work, for how long), so we don't know how hard...

I think this is the general problem here: risk factors do not simply sum up, they influence each other, and one cannot draw a red line for single factors. 50m on air OC will be OK for me under benign conditions, but on a cold water night dive at an 80m deep wall with currents I wouldn't do 50m...

I bet one will see a lot more trouble and incidents when diving with buddies, particularly instant buddies, than diving solo. However we always must distinguish between minor incidents and fatalities, not only because the latter are obviously more important to avoid, but also because their...

If you're referring to Anthony and Mitchell: "Respiratory Physiology of Rebreather Diving", these recommendations were given for planned working dives on rebreathers. But they write they also ran tests on OC gear and the results were virtually the same, that some working dives with densities...

From these reports (as well as the previous years' and BSACs) I see that most fatalities are related to cardiac problems, low level of fitness, in combination with "being alone in the water" (group fell apart, diver with problem was alone). Now about deep air, if 150ft "deep" air dives were so...

Of course there were many fatalities when they chased deep air records in the 1990s when Gilliam made his successful 450ft record air dive, and the 1980s with Exley's cave dives to 360ft with air. That was far deeper than the range you're discussing here. They wouldn't have called 150ft "deep...

IIRC, IANTD Advanced Recreational Trimix certifies you to 51m / 170ft, whereas Advanced Nitrox is only to 42m / 140ft, isn't it? Anyway, the classes are almost the same. So it makes sense for the student to take ART instead of AN no matter what he's diving after class.

Buhlmann's experimental dives in lakes and ocean were done to 350m (1150ft). He worked also with Hannes Keller, for his record dives to 230m (750ft) in 1957 in the Lago Maggiore, and to 305m (1000ft) in 1962 near Santa Catalina island. Buhlmann's work was funded by Shell Oil. They were not...

How about this concern: you guide an inexperienced customer first time into a cave and he stirs up silt and panics. Or there's some other "minor" inconvenience such as getting lost for a short time, swimming into a dead-end, and he panics. I think this is more likely than most gear failures and...

Yes it should matter a lot. The question whether your first deepest stop is too deep due to loading slow compartments depends a lot on whether you do that stop on 18/45, air or EAN50. Therefore any strategy of choosing GF_low independent from gases used doesn't make much sense to me.

OK got it. I'm all for clarity of the definitions, can only make the discussion easier. When calculating the gas in IANTD class, MOD and END were both considered, I didn't notice that "best mix" refers only to MOD. So you would say that both air and 21/35 are best mix at 56m (185ft) with...

The link you gave were for SDI Nitrox class, of course without helium. See for example: Custom Mix vs. Standard Mix: Best Mix is a question of balance - SDI | TDI | ERDI they don't make that distinction for deeper dives with He, best mix / custom mix / optimal gas all the same, END and MOD are...

Now you confuse me. You don't call a gas "best mix" because there's helium in it? These best mix calculations lead to the easy mixing of banked EAN32 and He instead of O2 blending for dives below 30m: At MOD with pPO2=1.3bar and END=30m (pPN2+pPO2=4.0bar), you get pPO2/(pPO2+pPN2) = 1.3/4.0 =...

maybe time for another thread split ... deep air is not best mix. ^^this. Standard gas vs best mix is ease-of-use vs optimality (deco, cost per fill). A personal situation-dependent choice.

P.S. I'd say every best mix is EAN32+He because this gives the right END at any MOD. Standard gases are just a once arbitrarily chosen subset of best mixes. Regarding the argument of changing dive plans on a boat: say everybody has 18/45 on the boat and you're the only one showing up with...

This is all true and convenient, but works with many mixes such as 28/15, 26/20, 24/25, 22/30, 21/35, 19/40, 18/45, ... Standard gases are a subset of these. Others like 30/30 are not in this set.

Buehlmann's experiments included chamber dives to 575m (1890fsw). His model was particularly developed for very deep dives.

So you lead and the beginner follows, swimming behind you where you don't see him. Not good. Why not swim next to each other along the line? The diver in the back is actually solo diving. He may be in serious trouble but nobody notices. If you had swum for 20s longer before looking back...

When you look at the DAN Annual diving report (2018), the largest group are men aged 50-59, but as long as we don't know the distribution of the overall diving population we don't know the risk. Regarding the solo diving aspect of fatalities, most dives in DAN list "Unknown", while among the...