Deco with too less air, options from the book

[MXGratefulDiver]

You are following your dive plan when someone else makes an error and you have to consider sharing gas. Perhaps you can abandon a stranger to his/her fate but suppose it is your wife/husband or your best friend.

For the sake of discussion I believe that satisfies your criteria.

I'm afraid it doesn't. Even at a recreational level, you should ALWAYS conduct your dive in such a way that if you should have to share air with another diver you will have adequate reserves to surface both of you safely. This is one of the fundamental safety protocols of diving with a buddy ... and, unfortunately, one that is seriously overlooked by recreational scuba training agencies.

However, what the original post described is a dive with a mandatory deco obligation. Once you start planning dives that require deco stops, the planning rules become more stringent. Every agency that trains people to do this type of dive emphasizes not just adequate reserves, but contingency planning for situations where one or more bottles may become unavailable to the diver. In other words, on a deco dive if everything goes according to plan you will surface with anywhere from one-third to one-half of the gas you took with you ... all that extra reserve was to accommodate just about any conceivable problem that you would have to deal with underwater. The reason is simply because you do not have the option of coming directly to the surface, and so you HAVE to deal with the problem while honoring your deco obligation.

I can appreciate that there are those who want this topic to stay focused on the theoretical question of which stops should be skipped. And I've provided my answer to the question. But I also understand the objection of those who state that this scenario just shouldn't happen in a deco dive ... they are right. If you follow your protocols for proper gas planning, you should be able to handle not just any conceivable problem, but any combination of two problems, without having to consider cutting your deco short because of a lack of gas.

That's part of the training ... and one reason why the training is so important.

Dive planning rules for deco dives are not the same as dive planning rules for recreational dives. There are many valid reasons for that. The most important being, simply, that a direct ascent to the surface can kill you.

... Bob (Grateful Diver)

 

[Blackwood]

I'm afraid it doesn't. Even at a recreational level, you should ALWAYS conduct your dive in such a way that if you should have to share air with another diver you will have adequate reserves to surface both of you safely. This is one of the fundamental safety protocols of diving with a buddy ... and, unfortunately, one that is seriously overlooked by recreational scuba training agencies.

I don't know if it's seriously overlooked by rec scuba training agencies. Rather, I think they tend to view surfacing as a good option in any rec dive.

 

[MXGratefulDiver]

I don't know if it's seriously overlooked by rec scuba training agencies. Rather, I think they tend to view surfacing as a good option in any rec dive.

Of course it is ... but that isn't really the point (you knew that, of course).

If sharing air with your dive buddy causes you to have to rush to the surface, then even on a rec dive you haven't planned your dive very well. If you haven't considered, and planned for, the possibility of having to share air with your dive buddy, then you've missed the whole point of diving with one.

But the rec agency's idea of gas management amounts to "look at your spg every few minutes" and "abort the dive at 500 psi".

That strategy doesn't work so well once you start accruing deco obligations ...

... Bob (Grateful Diver)

 

[Blackwood]

Of course it is ... but that isn't really the point (you knew that, of course).

I know. I just feel that trying to get the big agencies to shift from 'no stop' mentality to 'fix it in the water' mentality is a losing battle.

 

[TheWetRookie]

Yes on such questions I have some problems explaining it in english so it can be understood....
As more realistic example: in Croatia the "Francesa di Rimini" (not sure for the spelling) wrack is at 47 meter and some Dive Center go there with guides frequently. Usually they dive with a 15 liter tank and a short deco. It is seen as advanced recreational diving there (most have CMAS background not PADI). A lot safety there and as far as I know for all the years not a single accident ever happend.
But what if an very unlikey situation happens? (an accident). I can calculate the air usuage on land, I doubt I can calculate it under water while making the deco.
On the deco software it looks the best to move everything slightly up and slightly shorten it.
What me disturbs in the book is that thinking of which tissue to protect against bubbles and which not. While I understand the intention: "better have a problem on your skin than in your brain.", I can't figure out how the writer came to the result to better keep the deep stops and drop the shallow ones as a generell rule of the thumb.
I personaly don't do any deco dives which needs more than 2-3 minutes, but I think it is good to have a theoretic knowlege a few steps ahead of what doing in the real diving.

While the OP's question may just be a theoretical one, diving around at the depths he has posted should be planned for and not just taken for granted with bail out as an after thought.

Do you use deco software? What if v-planner wouldn't allow you to run a dive plan without proof of training to that level?
It amazes me that every time someone on here asks a theoretical question the "usual suspects" jump on the "get training" bandwagon. Well exploring deco theory is as much a part of training as learning gas management but those who don't really know anything about decompression feel the need to pontificate about something completely unrelated to the topic.
This could have been a thread I would have been interested in.

I beg to differ because from what I read in the OP's post #12, he is already doing this.

 

[texdiveguy]

I think ALLOT of readers missed #12 from the OP.....I replied to it on #14.

 

[wedivebc]

I beg to differ because from what I read in the OP's post #12, he is already doing this.

You mean this statement?

I personaly don't do any deco dives which needs more than 2-3 minutes, but I think it is good to have a theoretic knowlege a few steps ahead of what doing in the real diving.

 

[texdiveguy]

The OP I think added or tried to 'clear' his org. statement on #1. This thread got on and off course several times I think. I know I was confused several reading and I tried to follow it.

 

[orange_diver]

well i guess i'm late to the party, but isn't one plausible scenario a buddy who has a medical emergency at the start of deco? gas planning has nothing to do with it.

at that point a hard decision has to be made -- is there any room for me to shave time and get my buddy to help and if so where?

if i was to shave it would be at the shallower stops not the deeper ones. i would also try to hit as much of the oxygen window at 70' (on ean50) or 20' (on ean100) as possible and shorten others. i can live with skin bends and some joint pain and take a chamber ride. how much to shave, well, to be honest i really don't know? 10%, 20%??

 

[DaleC]

I'm afraid it doesn't. Even at a recreational level, you should ALWAYS conduct your dive in such a way that if you should have to share air with another diver you will have adequate reserves to surface both of you safely. This is one of the fundamental safety protocols of diving with a buddy ... and, unfortunately, one that is seriously overlooked by recreational scuba training agencies.

However, what the original post described is a dive with a mandatory deco obligation. Once you start planning dives that require deco stops, the planning rules become more stringent. Every agency that trains people to do this type of dive emphasizes not just adequate reserves, but contingency planning for situations where one or more bottles may become unavailable to the diver. In other words, on a deco dive if everything goes according to plan you will surface with anywhere from one-third to one-half of the gas you took with you ... all that extra reserve was to accommodate just about any conceivable problem that you would have to deal with underwater. The reason is simply because you do not have the option of coming directly to the surface, and so you HAVE to deal with the problem while honoring your deco obligation.

I can appreciate that there are those who want this topic to stay focused on the theoretical question of which stops should be skipped. And I've provided my answer to the question. But I also understand the objection of those who state that this scenario just shouldn't happen in a deco dive ... they are right. If you follow your protocols for proper gas planning, you should be able to handle not just any conceivable problem, but any combination of two problems, without having to consider cutting your deco short because of a lack of gas.

That's part of the training ... and one reason why the training is so important.

Dive planning rules for deco dives are not the same as dive planning rules for recreational dives. There are many valid reasons for that. The most important being, simply, that a direct ascent to the surface can kill you.

... Bob (Grateful Diver)

I agree with everything you say about proper gas planning and appreciate the way you say it. You managed to challenge my perspective without calling me stupid. In particular I agree with your implication that with proper planning nothing "should" go wrong which is far different than the notion that nothing "could" go wrong (the image of the Titanic comes to mind).

At the time I posted my comment I was thinking of that incident in which a group of divers drowned because one lost buoyancy and was too heavy to ascend. I don't recall the details exactly so don't quote me (I'm going to search it out and reread it now) but I was struck at the time by the fact that the instructor/guide died as well. I could imagine in such a situation (or something similar like a lost or entangled diver) that an instructor/buddy might feel compelled to aid someone under their care and put themselves in jeopardy by doing so (hence my example). It wasn't meant to be definitive.

Anyways, I'm learning a lot and always enjoy reading your posts.

Cheers.