NDL or deco dives

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fisherdvm

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I admit to be the dummest and dimmest diver on scubaboard. Took padi ow and aow 30 years ago, passed DM exam 10 plus years ago. And dumb enough when a diver asked me why his computer locked him out for a second dive from 55 ft... I did not have the correct answer three weeks ago. It is because I confused diving in the NLD means you are safe to ascend at ANY rate from ANY depth. Until I read in a deco training book that ALL divers dive using DECO procedures and rules do do decompression continuously. That breaking the recommended rate of ascend of 60 fpm early on, the 30 fpm later is the DECO time that MUST be obeyed or else you are at risk for decompression sickness, regardless of the nitrogen load your computer say. Okay flame away!!!
 
What do you mean by "NLD"? As for the computer question, there are some recreational computers which will have a snit and lock themselves out for any number of reasons. Without knowing more about the specific computer and what the diver did, it's impossible to say what happened.
 
He admitted to ascending very rapidly. No decompression limit modeling assume that slow ascent is obeyed. The theories state that we all have micro bubbles forming as we ascend, and their risk of coalescing is greater when we ascend faster than 60 fpm. Thus negating the safety margin built into the NLD tables.
 
Two years ago we had a group of aow students and their instructor dropped of on the east side of third reef in ft Lauderdale. Current was blowing all east ward and I was lucky enough to stay mid reef to fight the strong pull. The class was blown into the sand deeper than intended and surfaced with their computers locked up. We did not discuss the events with the class ... but they abandoned their second dive. I am guessing they did not go into mandatory deco but likely had at least one ascending too fast or blowing through a mandatory 15 ft safety?
 
Safe ascent rate is an important safety margin in recreational diving. With short enough bottom time and shallow enough depth this surfacing rate becomes unrealistically fast.

Ascent rate is taught along side every dive table I am aware of and monitored by most dive computers.

You're right though, even under an inch of water we're on gassing nitrogen and upon ascent we are decompressing.

Where this becomes practical to real world diving is for considerably deeper and longer dives.
 
OMG. I knew many recreational computers would lockout with blown deco but had no idea that some would do this with an uncontrolled ascent. I know its a “safety concern” but I think that computer would soon be on ebay...

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My computer manual allows dive instructors to shut off this safety lock out. As they have to chase out of control ascent on a regular basis. But it is a gentle reminder that achy tireness you feel after a day of diving could be dci/s and not just a strained muscle if you do not obey diving rules.
 
My computer manual allows dive instructors to shut off this safety lock out. As they have to chase out of control ascent on a regular basis. But it is a gentle reminder that achy tireness you feel after a day of diving could be dci/s and not just a strained muscle if you do not obey diving rules.
Lol. What about us Grumpy Old Divers that feel that way on a daily basis, with or without diving.

Locking you out is a bit more than a gentle reminder and seems a bit hypocritical to allow some to bypass this feature and not others.
 
Lol. What about us Grumpy Old Divers that feel that way on a daily basis, with or without diving.

Locking you out is a bit more than a gentle reminder and seems a bit hypocritical to allow some to bypass this feature and not others.
anyone can shut down the FAST criteria. But the guide suggests who would benefit from this feature - the instructor. We don’t give **** if our instructor stroke out or blow a lung! Actually it would be cool!
 
Sorry meant to say No Decompression Limit or NDL ... not NLD which is necrobiosis lipoidixa diabeticorum. Sorry!
 
https://www.shearwater.com/products/swift/

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