very interesting article, thanks for your work!

I have a question about your example, which I can not relly follow.

“…Note that for example it forbids to change from Tx18/45 directly to EAN50 (as He goes down by 18% of which a fifth is 3.6% while the N2 fraction increases by 13 percentage points, much more than 3.6)…”

If I switch from 18/45 to EAN50, my He drops by 45 points (1/5 = 9%) an N2 increases by 13 points, or do I have a mistake in my understanding? The result is similar, the N2 increase is higher than the He decrease, but not as much.

I would switch to a 50/15 in this case, but with 21/35 as bottommix a switch to EAN50 is mo problem imo ]]>

Interestingy, he also wrote: “when reaching this point (the deepest possible stop) during ascent from the bottom, the diver should slow down the ascent to the decompression zone rate of 10 msw per minute or less”. In other words: he assumes the first part of the ascent will be done much faster. When i remember Bühlmann right, he claims 10 meters/minute to be the maximum speed for all ascent in his model. While ascending, the tissues do offgas, the faster one more than the slower ones, and there is good reason to assume that Bühlmann has factored in this en route offgassing into the respective a and b coefficients. Thus, in case the initial ascent is done much faster, the fastest tissues will be brought bejond the limit of the Bühlmann model, and the only cure for this is to subsequently reduce their M-value, by introducing deep stops, calculated with GF factors…

Short, none exhaustive experiment using my dive computer’s simulation mode: GF off, 21/35 gas, bottom depth 50 meters, bottom time 30 minutes, all ascent with 10m/min. Result: the first stop will be at 15 meters, with leading tissue being tissue number 4 ! The tissues 1 -3 loose so much pressure during the ascent that they are not the controlling ones during any part of the ascent… But they will be in control in case of faster ascent, and then stopping wouldn’d be required at 15 meters but deeper — deep stops will be required then. So, to put it a bit into provocative words:

Are deep stops and GFs (at least partwise) the aswer to overspeed initial ascents?

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