PADI Deep Diver course- gas management

[steinbil]

I used 9m/min and a 3 minute stop which I find quite reasonable. If anything people are likely to blow past the stop under stress.

I don't think that's unreasonable. I think the most important thing is that people are taught how to calculate gas reserves, and that they use reasonable parameters that they (and their buddies) understand annd are comfortable with.

I do think it's better to err on the conservative side especially with newer divers, and it's very reassuring knowing that I have an ample gas reserve to handle emergencies.

However, my main gripe is with agencies and instructors that don't even teach or require any proper gas planning at all. I don't consider "be back on the boat with" to be sufficient planning, as the divers should understand and calculate themselves.

 

[Blackcrusader]

That’s a bit of a trick question. Using metric and American in the same question, instead of 11.1 litre for the size of the cylinder.

Not really. Anyone who has been taught should knows this anyway. People should understand both.

 

[Centrals]

Not really. Anyone who has been taught should knows this anyway. People should understand both.

LOL.
What system did they teach you in school?
Imperial(UK/US) or metric or chinese?

 

[Centrals]

That’s a bit of a trick question. Using metric and American in the same question, instead of 11.1 litre for the size of the cylinder.

It was NOT a trick question, it was silly.
A simple conversion and nothing to be proud of. Kid stuff.
I grew up with Imperial(UK) system and then have to adapt to the metric system.

 

[jadairiii]

I suspect he does not,

I'm still trying to understand this seemingly irrational fear of expanding the definition of "decompression diving"? At last check NDL's didn't come down from Mount Sinai.

If you have been diving for any length of time you know for a fact that mild symptoms of DCS goes unreported. So quoting DCS statics is problematic.

But, if you want a good start of actually understanding this premise, read The Physiology and Medicine of Diving, by Bennett. Or just continue to believe that diving within NDL is 100% "safe".

 

[boulderjohn]

At last check NDL's didn't come down from Mount Sinai.....

Or just continue to believe that diving within NDL is 100% "safe".

The straw man argument occurs when someone attempts to make a point by misrepresenting the opposing argument to make it easier to attack. It often does this by holding that misrepresentation up to ridicule. You are pretty good at it here.

No one implied that NDLs are sacred. No one implied that they are 100% effective. In fact, I specifically pointed out that some people do indeed get DCS when diving within limits. When I explained that studies indicate that most people who get DCS were diving within limits, that obviously means that I do not believe those limits are 100% safe.

I am sorry you feel your only recourse in discussion is to make an intentional misrepresentation of what others have said and then hold that misrepresentation up to ridicule.

 

[inquis]

And then of course you have plenty of data on divers getting bent on "no decompression" dives.

So quoting DCS statics is problematic.

Please forgive me, I'm confused by these seemingly contradictory statements. Is there "plenty of data" or isn't there?

 

[Cthippo]

Please forgive me, I'm confused by these seemingly contradictory statements. Is there "plenty of data" or isn't there?

There is enough data to be clear that it does happen, but not enough to really understand the risk.

 

[tursiops]

There is enough data to be clear that it does happen, but not enough to really understand the risk.

Bingo.
I've got 3300+ logged dives over many years, in most of the world, LOB, boat, shore, recreational, scientific, and technical.
So I've been in the company of at least 35-40K dives, between my buddy and the dive group I'm with.

• I've seen exactly one DCS case; it was a new diver on a 70 ft short dive....but with a massive PFO discovered after the fact. She is fine now, but not diving anymore.
• I've seen exactly one out-of-gas instance, managed perfectly by the diver the OOG person swam up to
• I've had exactly one OOG incident myself, in a cave (a second stage fell off my sidemount tank hose), with an instructor, and ending up taking her reg from her mouth for a few breaths while I sorted myself out.
• I've seen exactly two inadvertent buoyant ascents from 80 ft depth, with no residual after effects.
• I've seen exactly one HP hose rupture at depth (my wife) and she and I went together to the surface, slowly, each preathing from our own reg.

Kind of hard to do risk analysis....

 

[jadairiii]

Please forgive me, I'm confused by these seemingly contradictory statements. Is there "plenty of data" or isn't there?

No need to be confused. In the beginning, divers had no NDL tables. Then, USN developed their NDL tables, and life was good. But for some strange and unknow reason (data?) the large scuba instruction agencies just randomly cut anywhere from 5 to 10 min off those Navy tables. And then we all got computers, early computers used all the same algorithms that the Navy and large scuba instruction agencies used, and life was even better, well, maybe not. The early multi-level computers were a tad liberal (more data), like the SOS, Edge, Oceanic air computer. And again, for some strange and unknow reason, computers became more and more conservative. Ever dive an early Suunto computer?

All of this change could have been merely random....or lots of data. My "problematic" comment referred to those DSC incidences that were never reported. And I for one, am guilty of this.....

Anyway, whatever. But as stated, The Physiology and Medicine of Diving, by Bennett is a good read.

I would have responded sooner, but I was diving this weekend.