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This makes no sense. If they are "well within NDL", as you say, they can directly surface. The very concept of a "first stop" requires that you cannot directly surface, which is why GFLow is ignored until tissues are above GFHigh. As stated several times above, GFHigh determines the NDL.

@LFMarm, basic apps typically assume ideal gases. The Gas Blender Toolkit can do ideal or Van der Waals. You can run some scenarios to see the differences. (You can also confirm whether your current tool is/is not doing ideal.)

You're drawing a distinction when using GFLow values (the first of the pair), but that is irrelevant for NDL diving. Additionally, for deco -- when both are relevant -- you say "below" and then give a GFHigh that is above your limit. It's no wonder people can't understand you.

In my view, that's a lack of awareness. If it tells you to do unplanned mandatory decompression, you screwed up long before that point.

I can't tell what you're trying to say. Your first sentence says you would use a GFhigh above 70 for recreational diving. Then you state GFhighs of 75, 85, and 95 -- all above 70 -- are more designed for planned deco dives, which is NOT recreational diving by most people's definition. (Yes, the...

I use a transmitter or SPG/button -- not both. Anything that I might handoff to a teammate does not have a transmitter: deco stages, bottom stages, or backup diluent/bailout (CCR/caves).

I didn't compute Z, but the 77.x cuft spec for an AL80 is ubiquitous. That means Z > 1 and pretty close to 1.03. GERG gives that, DGX is similar, and even Wikipedia gives 1.03ish. The 0.88 value seems way off.

No idea why the disagreement, but Z_air @ 3000 psi is definitely > 1. That's why an AL80 (11.11L water volume) only holds 77ish cuft of gas when expanded to 1 atm. The ideal capacity is 80.06 cuft.

No experience with it, but it's a pretty simple device. Yes, I think you can count on those looks from charter operators. I don't know of any modern reg that doesn't fail open, but I'm not a reg expert by any means. As others have astutely pointed out, there are various issues that your...

https://oysterdivingshop.com/products/nautilus-t-adapter-300-bar-male-g5-8-2x-female-g5-8t-adapter-300-bar-male-g5-8-2x-female-g5-8 What are you worried about, in particular? Even for a free flow, you can still breath just fine as you're ascending.

Are you sure you need it? I leave mine loose to allow the manifold to rotate if it ever nose dives off the bench.

Yep. I have a monthly reminder to put mine on the charger, targeting 65% for minimal stress on the battery. Fully charge nightly or bi-nightly on dive trips, typically doesn't go below 50%. I have a USB hub, so charging everything (phone, DCs, primary light, etc.) just isn't an issue.

Exactly, right. If you're under GFHigh, you can surface (by definition). Shearwater and Garmin, for example, ignore GFLow for NDL dives. I suspect most others do as well, but it's easy to check if custom GFs are supported.

Nothing detailed, unfortunately. On one of the threads devolving into deep-stop bickering on CCRExplorers, Dr. David Doolette is quoted as saying: The NEDU deep stop study (NEDU TR 2011-06) specifically mentions the NMRI98 (gas-centric) and BVM(3) (bubble-centric) algorithms, but the above...

I believe that ISS is part of the pDCS calculation for [ETA: some of] the Navy's probabilistic algorithms. Researchers have also stated that ISS has comparative value for similar profiles.

One big reason computers are popular is they deal with multi-level profiles extremely well. If you had tried to plan your dive based on a square profile at max depth, your allowable bottom time would have been quite short. You could dive that reduced time, but why would you? Personally, I'd say...

Looks like you surfaced with a gradient factor of about 55% on both dives. That's well under even the high-conservatism default. Not an issue in my book.

@David Carron - Thanks so much for those runs. Generally speaking, there's a fairly consistent reduction in ISS of about 5-10% with a 6m final stop (compared to the 3m). The penalty one pays for this benefit is an average of 50-100% more time in the water. For a bottom-gas deco dive, though, I...

Thanks for the elaboration. I'd be curious as to the times and ISS values for a 80/80 ascent with last stop at a) 6m and b) 3m. That seems to be the front-runners, practically speaking. Oh, and which gas you assumed for those cases.

Please forgive me, but I vaguely recall that you were holding the total deco time constant, varying only the distribution thereof. Is that correct, and is that the time when the 3m stop is allowed? I guess at this point, I'm wondering about the surfacing supersaturation (gradient factor). Are...