How much gas in case of accidental deco.

[DevonDiver]

Gas management works for the anticipated. Redundant gas works for the unanticipated.

 

[tracydr]

My open water glass had rental gear with depth and pressure. Didnt even have a bottom timer come to think of it. The first time I saw a dive computer was when I rented gear for the first time and I said "Hey! Look at this thing!"

I thing with how much you pay for a computer, it should include a 10-20 minute 1 on 1 sit down with a KNOWLEDGEABLE rep that can explain how to use it...correctly.

How did you fill out your dive log without a bottom timer? Which agency? That would be completely against standard. Are you sure?

 

[watboy]

Living in SE Asia, i'm fortunate to get on 1-2 liveaboard trips a year. In the last few years i've witnessed 3 cases of relatively new divers going into deco according to their DC. They all had less than 100 dives experience and for each of them that particular liveaboard trip represented the majority of dives they will do for the entire year. I don't think any of them had an appreciation of how much shorter NDL's become on the start of your third day. And its not really hard to believe that by day 3, you get more relaxed, start to become a little complacent and just start following other divers around... until your dive computer starts beeping. And I don't think any of those divers had ever seen a deco screen on their computer before. One guy rushed to the DM, who ended up having to guide him through the deco stops to the surface. One guy was just puzzled and slowly surfaced with his buddy, showed a guide on the boat his computer and spent the rest of the day breathing o2. The third guy just assumed his computer was broken, continued the dive, and later when he discovered his computer was locked out, stopped wearing it and spent the rest of the trip just following the guide.

I understand that in the real world, people do exceed their NDL's, but in the above cases I don't think having a rule of thumb of how much time/gas deco requires, or getting a pony bottle would have helped. You would be best to put your efforts into learning how to understand what your DC's deco screen means and to dive conservatively if you are doing multi-day/multi-dive series and not ride your NDL's.

 

[freeclimbmtb]

I understand that in the real world, people do exceed their NDL's, but in the above cases I don't think having a rule of thumb of how much time/gas deco requires, or getting a pony bottle would have helped. You would be best to put your efforts into learning how to understand what your DC's deco screen means and to dive conservatively if you are doing multi-day/multi-dive series and not ride your NDL's.

While I do agree with this, and agree that in my previously described scenario, an extra bottle wouldnt have helped me either. Even if I didnt really know what I was looking at, I still understood my computer was telling me to get the F** below the ceiling...which I would have gladly done had I been properly weighted. (incidentally, I spent a few minutes trying to kick for the bottom in an effort to stay below the ceiling until I finally wore myself out and surface kicked back to the beach.) But as I have said now a multitude of times, that incident made me learn my computer and understand where I went wrong and how to avoid it in the future. Gas management, NDL, and weighting are things I now pay a lot of attention to, that coupled with understanding my computer and its features as well as its limitations, are the reasons I am only NOW asking questions about redundant gas, and decompression.

So would a sling have helped me then? Maybe, but only as dead weight...not as reserve gas.

 

[charlesml3]

What I AM negative about is people using them without knowing what the hey these things are telling them. I 've witnessed panic in divers because their computer told them they were in deco. Any decently OW diver SHOULD know what that means. If not, they are poorly trained.
I am not saying they should be deco experts... Just that they should know enough to realize what those numbers means. Only then will computers be worth more than expensive blingbling...

Well yea, I think we can all agree on that. But this has nothing to do with the presence or absence of a computer. If the diver doesn't understand deco and NDLs then all of the planning/monitoring is irrelevant, tables, computers or otherwise.

Heck, if anything I'd bet a diver would be MORE likely to respond to a beeping computer than happen to remember the NDL for a given depth/time while they're looking at a turtle.

-Charles

 

[TSandM]

I really don't understand what the issue with the OP slinging a bottle is. Although I prefer the concept of having a reliable buddy who plans and carries my spare gas, I realize that not everybody has the luxury of diving with known companions. A slung bottle has the advantage that it weighs less than a second full-sized tank, and doesn't require a manifold. It doesn't cause a problem on a dive boat that isn't set up for doubles. It's slung where you can check the pressure and see if there are any leaks. It is available for the diver himself, or for someone else, and can be handed off if the recipient is configured for and capable of carrying it.

Even with the training I have and the philosophy of diving I've adopted, if I had to do a lot of travel instabuddy diving, I'd seriously consider slinging a 40 for myself.

 

[boulderjohn]

Well yea, I think we can all agree on that. But this has nothing to do with the presence or absence of a computer. If the diver doesn't understand deco and NDLs then all of the planning/monitoring is irrelevant, tables, computers or otherwise.

Heck, if anything I'd bet a diver would be MORE likely to respond to a beeping computer than happen to remember the NDL for a given depth/time while they're looking at a turtle.

That is definitely true, and it is compounded by the fact that many divers have no idea what their computers are telling them.

I was diving in the Galapagos with a buddy I did not know well, someone who had signed up as a single diver for the same trip I had. he had several hundred logged dives, and he made sure everyone knew about his vast experience as a diver. We were going along, desperately hoping for a whale shark, when he suddenly started heading toward he surface, without even signalling me. I went up after him. When I got close enough to grab him (about 25 feet) and ask him what was up, I saw that he was wide-eyed with terror. He showed me his dive computer, a Suunto Vyper. I know that computer well. There was nothing remarkable on it. It showed he had plenty of NDL time left. He then continued up to safety stop depth, and I again went with him and gave an expansive "What's up?" gesture. He again showed me his computer, which had started to count down a 3-minute safety stop. I held the computer in my hand, showed it to him, and again shrugged. He looked at it for the first time himself, and he seemed totally puzzled.

Well, we both still had a pretty good amount of gas left, but there was no sense going down again, so we went up and got in the panga that was picking us up. There he excitedly said, "I almost went into deco!" It sounded as if he had miraculously escaped death. As divers surfaced and joined us in the panga, he continued to babble about his close call. I had to keep interrupting him to calm him down and get the full story. It seemed that when we were at depth, he had looked at his computer and seen that he only about 3 minutes of NDL left, and he figured it would take him at least that much time to get to the surface, especially with a safety stop. Hence his hasty ascent. I tried to explain as patiently as possible that he had only 3 minutes at that depth, and that as he ascended, he had been granted more time. I told him that the first time he showed me the computer, he had oodles of NDL time on it. He refused to believe it at first, but eventually the rest of the people on the panga were able to persuade him that I was telling the truth. I tried to explain his other misconceptions, too, but it was like the proverbial brick wall.

So, it would be very useful if people understood first the basic idea of decompression theory and next that going into deco is not a death sentence. Finally, it would be extremely helpful if people read their manuals or took a class so that they knew what they heck their computers were telling them.

 

[DaleC]

Be it as it may, I am GUE trained, these guys know what they are doing ( I'm NOT saying others do not) and I fully stand behind what they teach.

So in MY world... the manifold stays open because in my world there is no valid reason to close it...

But... to each its own...

My nice answer:

In my world, I dive with a wide spectrum of divers with a variety of skills and equipment configurations so some of those choices would put me at a distinctive safety disadvantage.

While confining my experiences underwater to a few divers who share a standardized outlook and who don't regularly do the dives I want to do would reduce that disadvantage, I would miss out on diving with a lot of people I enjoy spending time with and seeing a lot of things that really interest me. Personally, that price is too high, especially when I can more easily adopt diving techniques that provide safety in the conditions I actually find myself in. One of those techniques is complete redundancy for deeper dives which can easily be achieved via ponies, independent doubles or isolated manifolds. It's not really rocket surgery nor is it a faustian deal with the devil. It's just diving the way the majority of the world does it - instead of the way a small minority does.

And, suggesting that people carry ponies because they don't know about gas management is just foolishness. It's like saying DIR divers carry wetnotes because they can't do hand signals.

 

[lowviz]

Correction:

It has been brought to my attention that the "Decompression Procedures" course I suggested is not an IANTD offering. This is correct, it is TDI's ( TDI Home | SDI | TDI | ERDI).

Apologies for any inconvenience: Decompression Procedures Diver | SDI | TDI | ERDI

Please note that this is an informational-only course. It is my belief that this course gives the sport diver a solid understanding of what entering "deco" means and then provides a "no panic" path back from light deco situations. This course certainly does not equip one to begin technical diving. It just provides a measure of understanding and is an excellent way to cross over the "we can't talk about that" gulf between sport and tech diving.

 

[boulderjohn]

Please note that this is an informational-only course. It is my belief that this course gives the sport diver a solid understanding of what entering "deco" means and then provides a "no panic" path back from light deco situations. This course certainly does not equip one to begin technical diving. It just provides a measure of understanding and is an excellent way to cross over the "we can't talk about that" gulf between sport and tech diving.

I have no idea what you mean by this. I certainly think it equips one to begin technical diving. You learn to use decompression procedures with a decompression cylinder. That is definitely within the realm of technical diving. The next step in the TDI realm introduces helium.