Sharing air & continuing dive???

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.

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

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?

There's nothing wrong with that as long as you are dillgent in monitoring gas and understanding how much you need to safely return to the surface - don't dip further into your tank than you'd both need to surface on your gas. It's hardly different (fundamentally) than bringing a bigger tank.

Not a bad Idea at all. I've got some friends who call it in flight refuelling and do it on most dives. You've got it right that it is an idea best practiced early in the dive in case the donor has a gear failure the air hog still has reserve. A five to seven foot long primary hose also makes this a lot more convienient

Sure, why not! But do it before your tank is low. Early in the dive makes sense. That way you both have enough air individually to get both of you to the surface.

Or get a bigger tank...

Richard

It's OK but makes gas planning more complicated since it'll be harder to know the actual gas consumption rate for either of you individually. Plan your low air limits with sufficient air for either tank to get both of you to the surface.

BTW- managing air this way will probably cause increased effort and yet even higher consumption, possibly negating the benefit. The best bet is a larger tank, or improving your dive skills to lower your gas consumption.

I can see the sharing air at the beginning of the dive maybe, but I'm not sure how that really helps, unless one buddy has a significantly larger tank. Seems cumbersome anyway. But the original example was that one buddy ran out of air and they shared in order to continue the dive. What if a one in a thousand chance happens like equipment failure and they are both out of air now. Are they shallow enough for a CESA? Kinda like diving solo but with another diver attached to you. There is also the remote possibility of entanglement or entrapment. I wouldn't do it.

I think it is a good idea. My wife and I do it to extend our dives. But we start not lower than 1000 psi on the recipient diver and stop when the doner hits 1000 psi so there is always plenty of gas in both tanks.

awap:

I think it is a good idea. My wife and I do it to extend our dives. But we start not lower than 1000 psi on the recipient diver and stop when the doner hits 1000 psi so there is always plenty of gas in both tanks.

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That makes sense to me.

As long as BOTH divers end the dive with enough air to get BOTH divers to the surface.

Another poster suggested a larger tank. I have not dove anything larger than a 100. As I am not a big guy a 120 might be a bit big for me.

Also, the suggestion that the additional effort may negate the benefit: If we are at 85' and I have 800psi and my buddy has 2400psi. We can end the dive or we can share air and extend the dive until my buddy is down to 1000psi and then end the dive. Benfit? We extended the dive beyond where it would have ended otherwise.

I'll ask again though, any safety concerns if I am down to 1000psi and my buddy has 2400psi, we share air until my budy is down to 1000psi then end the dive??

mohave_steve:

I'll ask again though, any safety concerns if I am down to 1000psi and my buddy has 2400psi, we share air until my budy is down to 1000psi then end the dive??

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Depends (inert gas loading, depth, consumption rates, tank volumes), but for most profiles probably.

As suggested above, I can see the two of you sharing her air near the beginning of the dive. You both know your relative consumption rates and can work out a dive plan to share her air for say the first 1000 lbs, then go to your own. Doing this you can benefit from her "extra", but by doing it this way as you continue the second phase of your dive plan you each have relatively full tanks. You avoid entering into the second phase of your dive with an already depleted air supply.
Probably you will never get into problems sharing later, but the risk is there that should something unforeseen strike during the latter phase you each have enough air to work through the problem if you are not in the position to immediately ascend. Might never happen, but.....
Plan to minimize the risks as much as possible, cause when s*#t happens, it's always at the worst possible time!!!