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If scuba instructors teach from a book then we could be in trouble with this. From SSI's science of diving course book (copyright 2010) under the section on dive computers from the chapter on decompression theory we have this: "Going deep, then shallow, then deep again will yield unreliable...

While we don't have access to the exact algorithms employed in the dive computers, Bruce Wienke wrote a paper on the RGBM model. It is included below. Beyond all the initial pages on the math he has some interesting comments at the end of the paper.

While some slow TC's (tissue compartments) on gas, especially during deep deco stops , they may not on gas to the point of being the CTC (controlling tissue compartment). The amount of on gassing is partly controlled by the TC's half-time. Since TC's 14,15, and 16 have such long ht's they...

One interesting point is that the process I describe above continues on the surface. Once the TC's have saturated at ambient pressure the computer probably stops calculating TC pressures and ceilings until there is a substantial ambient pressure change (ex. ascending to lower pressures or...

I don't have access to Suunto's dive computer code. Most, if not all, the commercial personal dive computer algorithms are proprietary and are not available for scrutiny. I can tell you how Erik Baker's (Fortran) and my Excel spreadsheet (VBA) work as these programs are in the public domain...

If you put your mouth over the valve that could happen. We were told to breath from the bubble stream; your mouth did not touch any part of the valve. I know it's weird but it works. You would think you would get water forced into your lungs but you are over the valve so the water does not get...

I wasn't thinking of bubble growth. However, a lot of the inert gas bubbles have been washed out by the O2. I read something about oxygen DCS. Has this happened? Is it true? Or, is it something theoretical?

Wow! 1 fpm. That seems agonizingly slow and agonizingly unnecessary. I don't dive with pure O2 but I think once you're cleared to go to the surface you stay on O2 all the way up. Since you're not taking on any inert gas what's the point of making such a slow ascent? Edit: I posted this before...

I got certified (Basic, not OW) in 1974 from NASDS. As part of getting certified we had to do exercises that would make the SEAL's proud. With all of our equipment scattered at the bottom of a 12 ft pool, we had to dive to the bottom, assemble our equipment and put it on, before going to the...

Using my spreadsheet I compared two dives, both to 250 ft for 20 min, at a descent rate of 60 fpm, using a GF of 60/85 on trimix 20/40. One dive used an ascent rate of 30 fpm for the entire dive. The second dive used an ascent rate of 120 fpm up to 100 ft which was the first stop and then 30 fpm...

Your example above highlights the issue with reverse profile dives, that they are inefficient. If you need time (i.e. more NDL) at the deeper depth you need to do the deeper dive first. PADI understood this but as time went on the admonition to avoid reverse profiles became stronger until...

I don't think I would want to get close enough to stick this knife into them if that is even possible. I would prefer something longer like a bang stick. The ad for the knife says it's useful against large land predators like bears. Again, I don't want to be that close. My advice: get a gun.

In today's highly charged political climate AAA must stand for: A(nd) yet A(nother) A(ctivist) We need to protest that there are too many firefighters standing in the way of oncoming cars. :wink:

A while ago I read a book on sharks by an expert (I don't have the book and don't remember the title or the author's name), who agreed with you. He said that sharks are curious animals and if so inclined will bite in order to taste with their gums to determine what the creature is and possiblly...

What I recommend all NDL divers do is set an alarm on your computer to notify you when your NDL is under 5 minutes. You can do this on the Perdix. A visual reminder is good but in addition a vibrating warning is best if you get distracted and don't look at your computer.

So, I confused surface interval with half-time. I must be watching too much football. You posted this information in another thread. I should of looked it up first before posting but I got lazy.

No. This is wrong. The PADI tables, I believe, are based only on one tissue compartment with a half-time of 120 minutes. Dive computers using ZHL-16C incorporate 16 tissue compartments with varying half-times of which any one compartment can be in control of the dive based on the dive profile...

Based on @rddvet and the above response I feel I might have been misunderstood. I am not criticizing anyone for getting bent. I was simply pointing out that saying something negative regarding something you are trying to persuade someone about works against you. Paraphrasing @oya, "I believe...

I'm sorry you had to go through so much trouble before finally finding the cause, but what has this got to do with my comment specifically, and what we're discussing in this thread in general? The question is whether average depth and/or the modified rule of 130 is safer as a backup to diving...

It looks like he's breathing from a tube extending up from the goat bag. If that's the case, why is he breathing from a bag if he is just floating on the surface?