Safe ascend with empty tank.....

[fisherdvm]

I started a thread under "tanks bands, etc" under the heading "How to ascend with spare air" with the hope of discussing the safest way to ascend with the residual air in an empty tank with or without spare air.

I hope that people with knowledge in diving physics and medicine would browse and contribute.

My question was with the limitted amount of left over air (0.3 to 1 cu ft) from the empty tank. Or with the addition of 2 cu ft of air (actual from a spare air 3 cu ft tank), where would be the best place to start using that precious little air. Should it be used continously as one ascend, or to save that last bit at 15 ft to get 1 to 2 minutes of decompression.

Please contribute at the other site if possible ..... We were hoping to avoid the "pony vs spare air" battle, or "why are you stupid enough to lose your buddy", or "why did you not watch your tank pressure" comments.

Thank you....

 

[cornfed]

Honestly, I dont' think it matters. If you're diving within the "no decompression limits" they you should be able to make a direct ascent to the surface without any serious complications. So you'd be best using whatever gas you have left to make as slow and controlled ascent as possible.

That said...

 

[scubasean]

Honestly, I dont' think it matters. If you're diving within the "do decompression limits" they you should be able to make a direct ascent to the surface without any serious complications. So you'd be best using whatever gas you have left to make as slow and controlled ascent as possible.

That said...

I think Drew means..."no" deco limits...heh

I think if you are that low on air the best thing to do is to safely ascend, and get to the best air supply available (the atmosphere...).

Though both are *bad*, running out of air and dying is infinitely less preferable to DCS.

 

[lamont]

is the answer you're looking for that you're better off using what air you've got when you're higher up in the water column?

clearly you can ascend faster with fewer problems when you're deeper -- the last 10 feet are the most critical to ascend slowly. also, you use air faster when you're deep.

so, if you're nearly OOA its going to be better to exhale and ascend as much as possible before taking another breath. if you've got gas to hold a 15-10 ft safety stop clearly it'd be better to hold that as long as possible before surfacing.

but in an emergency situation, i don't know that you can count on sucking your tank dry and effortlessly ascending 30 or 40 feet, deploying your spare air and taking that first breath. for the purposes of planning an emergency i think its stupid to be thinking of this as an option you're likely to have. trying to rationalize the use of a spare air this way is just going to get you killed when it doesn't work out the way you planned. however, if you run into this option underwater, clearly you're going to want to try to take it.