Sharing air & continuing dive???

[SteveAD]

You all may beat this around all you like. If you want more air, carry more. Don't plan to use your buddy's air. This is not good as your dive plan.

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You keep saying this and refusing to acknowledge that tank size may not be a variable. Most of us have our ideal size tanks when we are diving at home so both buddies use a similar perecentage of their own tank on the same dive, but when we travel, many resorts don't offer much variety on tank sizes. So if two people with dissimilar SAC rates are both stuck with AL 80s you still insist that the sipper end the dive while their tank is still half full so that the hoover can end with a 500 reserve.

Assuming that we are talking about an experienced buddy team (like Peter and Lynne) who know each others SACs very well, and share early and never cut into either divers reserve I fail to see your objection.

If you want to surface when your tank is still half full any time you are buddied with a hoover, that is your perogative, if you want your buddy to surface with a full tank because you've sucked yours down, please don't ask to dive with me.

 

[diver 85]

Many years ago, I used to dive that way with our daugther(she made air down there as a 14 y.o.) This air sharing is done all the time between DMs & customers on Carribbean trips ie drift dives on CZM(in general, the group dive is called when the 1st diver needs to surface)....----People travel that far & spend that much money, they want as much BT as possible.......

 

[Thalassamania]

I wasn't indicating that YOU were doing something wrong... I believe I said that in some circumsnatces I can see this being acceptable; however the original Post:

A while back I read an account of a diver who ran out of air during a dive, signalled his buddy to share air and continued the dive until they were down to 500psi at which time they surfaced together.

I'd agree, not the best procedure, which would be to share air a bit earlier in the dive.

IMHO that was dangerous behaviour. If I or my buddy experience an OOA situation the dive is over.

Agreed for a number of reasons.

Two weeks ago I was diving with a buddy who has a SAC rate that is substantially (1/2?) lower than mine. I was diving an HP100 and she was diving an HP80. We were at 85' when I hit 800psi and signalled time to surface. We did a stops at 45' and 20'. I was back on the boat with a bit under 500psi. My buddy still had 2300.

She offered to share on future dives. My initial thought was "no way". Air sharing is for more urgent circumstances. Not to allow Hoovers like me to extend dive time.

After thinking about it a bit I wondered: What about begining sharing while you still have 800-1000psi and then returning to your own air when your buddy hits 1000psi and ending the dive? Something tells me it would still be a bad idea but I haven't come up with a good reason why.

Any thoughts?

IMHO, The earlier in the dive that you share the better.

I'm not asking the OP to skip breath and increase risk... I'm hoping that they realize that this variance in breathing rate may require looking into... a reasonable statement I think - that BTW is coming from someone who is fairly heavy on air myself...

I agree.

Sure... and you can "if" a lot of other items away too..., I don't believe this is in line with the original post, or is helpful, and really, is simply inflamatory IMHO.

YMMV

I guess I'm confused ... what's inflammatory about a simple statement of fact? When we've been above the arctic circle we often dove independent doubles or slingshot valves so the we had fully redundant rigs. This is off topic and I don't want a big hijack, but I'd like to know ... am I missing something?

 

[JMcD]

I guess I'm confused ... what's inflammatory about a simple statement of fact? When we've been above the arctic circle we often dove independent doubles or slingshot valves so the we had fully redundant rigs. This is off topic and I don't want a big hijack, but I'd like to know ... am I missing something?

If you are trying to outline circumstances that would make the practice of sharing air simply to extend a dive (to balance out air consumption between a dive team) acceptable to you, then I understand.

However, as I see the original discussion/posting, the discussion is essentially asking about doing so based on a pretty much a standard set of gear... I simply identified a risk for many that doing so can cause significant air draw through a first stage that can led to a free flow in cold water diving - while I agree that it, like many other problems can be mitigated, I wanted to make sure that divers who may not know better didn't simply think it was without risk, do it and then get themselves screwed just because of misinterpreting a thread on SB.

To jump on that to identify why it is wrong and can be mitigated by the right gear configuration I believe misses the point of my post and potentially just sets off a "if the rig is set up this way then all things are better... etc etc etc..." type of post which I would hope to avoid. (hence my use of the term "inflammatory" )

I believe this is a good discussion and would hate to see those who love to fan that flame take over...

 

[Thalassamania]

To jump on that to identify why it is wrong and can be mitigated by the right gear configuration I believe misses the point of my post and potentially just sets off a "if the rig is set up this way then all things are better... etc etc etc..." type of post which I would hope to avoid. (hence my use of the term "inflammatory" )

I believe this is a good discussion and would hate to see those who love to fan that flame take over...

Sorry, that was not my intent at all, I have started a new thread: Does extreme cold water diving call for fully redundant regulators?

 

[redacted]

The source problem may be not be a "problem" that needs working on. I can nurse a tank and get to a SAC below .30, what do I get? A longer dive with a bad headache and a slew of problems that increase the risk of the dive, I make a conscious effort to stay above .50 and I like to keep it as high as 0.7.

At the risk of drifting off topic if we have not yet beat this to death, besides headaches (and longer thermal exposures), what other problems are you talking about? I don't think I can get down to .3 but I do regularly get down in the .4 zone (I plan at .5). I've never given myself a headache from underbreathing. Can you get too mellow UW?

 

[Thalassamania]

I first started trying to raise my SAC after some headaches and a rather bad case of Dark Narc, It seemed to help. Then at the suggestion of several authorities in the field that I should strive to keep my CO2 down I decided on a target range of 0.5 to 0.70, and its seems to have worked well for me.

 

[TSandM]

Some of us are very CO2 tolerant -- we don't get the anxiety response that makes you breathe more. I'm one of those people, and I believe Thal has said he is, too. I've had to make a conscious effort to breathe more to avoid headaches.

But regarding the "gas consumption problem": I'm 5'4" and 120 lbs. My regular dive buddy is 6'1" and very strong (i.e. lots of muscles mass). He's a FAR better diver than I am -- dead quiet in the water, pinpoint buoyancy control -- but his SAC rate is half again mine, and always will be. And should be.

And Peter's SAC rate is higher than mine, and should be.

Once you've gotten smooth and quiet in the water, SAC is mostly determined by metabolic rate, which is heavily dependent on size and muscle mass. Bigger, stronger people are going to have to breathe more -- that's all there is to it.

 

[Thalassamania]

I am very CO2 tolerant, likely comes from years of freediving. When I was young and macho I thought it a good thing, in my thirties I discovered that was not the case ... fortunately it was the headaches and need to control the Dark Narc that taught me to fix things, not DCS or OxTox.

 

[Couv]

Thanks Awap, Lynne and Thal for bringing this to light. I too have a very low SAC (can I say that?) and sometimes get headaches. Others have commented, "You must be skip-breathing" but that is not the case-I have made a conscience effort not to. However, I have not thought of making an effort to target a higher SAC.

Cheers,

Couv