Dive computers are untested and unsafe?

[DevonDiver]

It is worth pointing out that there are two tables/models (in general use) actually based on experimental data (and can be called safe): The original Navy Tables, and the RDP. All dive computers are based on theoretical models without real world testing, so diving anywhere near their limits is acting as your own experimental subject. There is essentially no grounds to claim that any computer is safe, because none of them has experimental data behind it.

Discuss...

[knowone]

The point of diving is to test things

[halemanō]

I have been diving my current computer for going on 8 years and a few thousand dives. It has been pushed to it's limits, and beyond, more than just a handful of times. I have also seen other brand computer users staying deeper and longer on multi dive days than my computer will allow me. Most of the operators I have worked for and rent gear from supply the same brand computer as I own, so the other brand issues are few.

The proof is in the puddin'

For more than a decade the various modern dive computers seem to be bending not enough more percentage of divers than the tables to be reported about, unless you are about to direct me to such a report.

[=C=]

Uh yor statement contradicts itself.. There either is or is not data to back up a finding. That's how science works. The test subject is not you but rather the first divers who tested the tables. Further, we understand the principals of gas absorption which is at the heart of the NDL.

The "controversy" with dive computers, if you can call it that, revolves around that it uses theory to predict loading not an actual sample of your blood checked for bubbles. The science is tested however in action we have not come upon a way to actually measure n2 load in the blood during a dive that is convenient.

Diving "near the limits" you are making assumptions about your body and not about the science.

[Dsix36]

It is all just VooDoo.

The deco models have no hard proof behind them. Most have been derived via trial and error over many years. The original navy tables were great if you wer 18 years old and healthy as hell, but the real world divers were getting bent. The newer deco models have tried to take into account that 600 pound, lazy, people will dive too. This is why most algorythms will allow a diver to adjust their conservatism to suit themselves.

Many of todays computers use their own priorpriatary algorythms and it can be very difficult to make differnet ones match deco profiles, if at all. Which one is right? Both? Neither?

I chose my computer because I understand the algorythym and how the different conservatisims work to adjust the deco profile. In the end I am just another guinea pig though.

[drbill]

I'm definitely not a healthy 18-year old any more, but I've done thousands of dives on my computers... pushing them to the limits (a number of dives to 200 ft and averaging 180 on three dives one day). Never had an incident (yet). However, whenever possible on a deco dive I extend the time... letting my gas supply determine the amount of deco and giving me added time to film in the shallows. I can't say that the algorithms used will work for everyone, but they seem to work fine for me.

[Peter Guy]

DevonD -- Beano is correct (as far as I know) -- and it may well be "VooDoo" to a large extent. It was fun to listen to Dr. Deco talk about the NASA research and how they never could identify a number of issues.

BTW, just because we may not know why something works, doesn't mean that it doesn't work. Science may well NOT be "the answer" whereas trial and error is.

[Dsix36]

I will trust tested trial and error over science any day.

[TSandM]

Several of the tables have been extensively tested. I don't know what testing has been done on any of the computer algorithms. Rubicon might be a good source for information about that, if you can figure out how to phrase the search.

[Mr Carcharodon]

There are just two tables/models based on experimental data? What about Haldane, Hawkins, Yarbrough, Van der Aue, Buhlmann, BSAC, DCIEM, NAUI, and VPM? Do they not count? Or are they not commonly used? Or were they not considered? It would appear that all of these have various degrees of experimental grounding. There seems to be less that one case of DCS per thousand dives which seems to be a success rate well outside of voodoo territory.

It is hard to know if a given computer is safe since the manufacturers typically do not share the details of what they are doing. That said it appears what is commonly done is to use one of the more modern models listed above as points of departure, and then the algorithm is typically made more conservative. How well that works out is hard to say since there is not generally data. Also it is possible to go too far the other way. Some manufacturers have a penalty for cold water. While in principle that may make sense the dive computer does not have insight into how well the divers dry suit is working on a given day or even if a dry suit is being used. So the implementation at times is dubious.