How Much Gas is Enough - Running on Empty (Ainslie)

First I want to say thanks for having the courage to tell everyone about this dive. You are indeed very lucky that the chain of events finally got broken and you made it out safe.
It often seems that when something bad happens it is often a series of decisions that are made upon one seemingly insignifcant one happening and then it spirals out of control.
Although I am not cave certified, hope to start on it in 2011 I have always looked at air as being a commodity I can not do without.

As soon as I started diving I started using a 30 cu.ft. pony on all dives that would give me and anyone else somewhat of a safety net if anything happens. I have been in positions fighting fire where air can go quick. We used to use 30 min rated bottles before switching to 45s and I have seen times where they could be emptied in less than ten minutes and have seen some as low as 5 mins.

Reading this will definetly make me look at gas even way more than just thirds becuase nobody knows will the little gremlins or diver murphy will be with me or anyone else.

Again thanks for sharing this and I hope you never experience this again. I also hope it will prevent some one else from having an accident that can be prevented by just having enough air and taking the time to analyze every problem.

Thanks for the very enlightening article. Obviously, I need to join NACD to get more of the same. I assume those of us with just the Cavern card may join.

Tom

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Originally Posted by TONY CHANEY

.. why did you continue to drag around, what you believed at the time to be useless, equipment that was creating more drag, additional weight and making restrictions more difficult? ...

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I am sure Andrew will answer, but besides the "head problem" he had, removing equipment can wreack havoc on your buoyancy and trim.

I know that you know far more than me but I thought that trim issues while removing gear is one of the pros of sidemount. Also, it seems that trim was not an issue removing and staging 1 oxygen tank and 2 80's.

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Originally Posted by TONY CHANEY

I know that you know far more than me but I thought that trim issues while removing gear is one of the pros of sidemount. Also, it seems that trim was not an issue removing and staging 1 oxygen tank and 2 80's.

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You are right about stages and O2, but 85s are pretty heavy, and would greatly change your buoyancy. Depending on what rebreather, it probably would require removing all the other gear to get it off, then you run the risk of floating to the ceiling, and having your tanks on the floor.

FWIW, I would dump any empty stages, but not my side tanks or back/chest mounted rebreather.

Sorry, I wasn't sure exactly how a SM rebreather is mounted. I thought that in sidemount the diver is weighted in order to prevent going to the ceiling while in a no mount configeration. Now the 85's would have been dropped. Simply if you don't need then don't bring it. But I am still learning from divers such as you and Andrew.

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Originally Posted by FW

Not generally. He didn't run out of scrubber, he broke a hose in a tight tunnel. That would have flooded multiple scrubbers anyway. It is pretty easy to calculate scrubber duration, so you just time when you need to turn.

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Ideally, it would be something that would be sealed until it was needed. If it is easy to calculate duration, then 2 should be sufficient, and dive each to 1/3rds. Seems this would lend well to a SM RB config too.

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Originally Posted by Greenwood_60

Ideally, it would be something that would be sealed until it was needed. If it is easy to calculate duration, then 2 should be sufficient, and dive each to 1/3rds. Seems this would lend well to a SM RB config too.

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Simplicity is the key. Rebreathers are complicated enough, without having to switch scrubbers during a dive.

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Originally Posted by TONY CHANEY

Sorry, I wasn't sure exactly how a SM rebreather is mounted. I thought that in sidemount the diver is weighted in order to prevent going to the ceiling while in a no mount configeration. Now the 85's would have been dropped. Simply if you don't need then don't bring it. But I am still learning from divers such as you and Andrew.

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If you plan to go no-mount, you can weight yourself for no-mount, but I think Andrew was just using the 85s for bailout. As for how sidemount breathers attach, there are very few that have the counterlungs in the same container as the scrubber. Those can be removed fairly easily.

IIRC, Andrew's is actually a modified backmount, and he was wearing the counterlungs on his shoulders, under all the other gear.

I think the biggest issue here was time-pressure messing with his head, and he wasn't thinking clearly.

As always, thanks FW. I figure that Andrew would be able to shed so light on this. I would really need to see it in order to get a picture in my mind.