What are Mathematical Decompression Models?
- Thread starter carloslzn
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Where did you hear this? I'm not aware of this "rule."
Sent from my SAMSUNG-SM-G900A using Tapatalk
Sent from my SAMSUNG-SM-G900A using Tapatalk
victorzamora
Contributor
I think this is a misinterpretation of a recreational table. Those aren't built for deco, have "exceeded ndl contingencies" that often involve staying dry for a prolonged period. It could also be a carry over from military practices (though unlikely).
OP: Many/most deco divers do repeated deco diving. I've done four deco dives in a day and frequently do two.
OP: Many/most deco divers do repeated deco diving. I've done four deco dives in a day and frequently do two.
Get a copy of the book Deco for Divers by Mark Powell. It will answer all your questions and more. It's not as difficult to read as it may sound. Even a beginner diver can understand it.
Mustard Dave
Contributor
This. I make repetitive decompression dives all the time, as do countless others.
The PADI OW manual says that if you exceed a no decompression limit by less than 5 minutes, you should ascend to 5 metres no faster than 18 metres / minute and remain there for eight minutes. After surfacing, you shouldn't dive for at least 6 hours. If you exceed an NDL by more than 5 minutes, you should increase this to no less than 15 minutes, gas supply permitting.
If you are following a deco computer or deco tables, there is no reason why you cannot dive again, but as the PADI tables do not factor in decompression, you could not use them to plan a repetitive dive.
Ah, I see what you're saying. Yes, I suspect that's what's going on here. Perhaps the question could be more clearly worded as: "Why should a diver stop diving for at least the rest of the day if, on a dive that was planned as a "no-decompression dive," the diver inadvertently exceeded the no-decompression limit, thereby requiring an "emergency" or unplanned decompression stop?
---------- Post added January 29th, 2015 at 09:00 AM ----------
Add Mustard Dave's clarification that this applies to table diving, not computers.
Mustard Dave
Contributor
Correct. However, any Suunto computer, from entry level like the Zoop to more techie ones like the HelO2, will track your deco on one dive and compensate for it on a repetitive dive (I chose Suunto as they are the most common choice for recreational divers in my part of the world). If you really upset it, such as by coming up like a Polaris missile and/or missing a mandatory deco stop, they would lock you out of a subsequent dive.
I haven't seen the OW manual since the program allowed computer diving with no table / eRDP planning, so I'm not sure what they have to say, but I do still suspect the myth about not diving after a decompression dive has it's origins in dive planning using no decompression tables.
If this were actually the question, then the answer is simple: for a moderate exceedance, stay out 6h to (1) let most of any DCS symptoms appear, and (2) let the slowest compaertment (1h) "clear," i.e. 6 times the half-life. For a major exceedance, stay out 24h to (1) let almost all of any DCS symptoms appear, (2) get "clean,"" of N2, and (3) sit in the penalty box for a day because you really screwed up.
The PADI computer-based OW program tells students that if they accidentally violate no stop times on the computer, they should follow the computer's plan for decompression. This means, of course, that divers should know how the computer will guide them before they get in the water with it. That is a real value to the course. It specifically identifies the functions on dive computers that students should understand when they get one. That allows them to look for specific critical information in their manual when they get it.
... moreover, it's important that divers not only understand how the computer will guide them in a deco dive, they should also understand the critical aspect of gas consumption and how this should be accounted for if they choose to "ride" their computers into deco and want to get out of the water safely. Redundancy is yet another aspect.
Even in NDL diving where crossing the limit and having a small amount of mandatory deco, it's still mandatory - whether it's 5 min or 55 min. So all of these aspects need to be considered when you cross the NDL threshold.
Even in NDL diving where crossing the limit and having a small amount of mandatory deco, it's still mandatory - whether it's 5 min or 55 min. So all of these aspects need to be considered when you cross the NDL threshold.
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