[David P]

so I shouldn't say anything about being @ 120' on a single 80, leaving your team mate, especially one that is impaired, use of helium (it was 20 years ago)?

another post a few up said always dive with a pony rig... what size, hopefully a 40. Do the math on a 100' dive with an Al80. Figure your at 4 ATA, the fit hits the shan, so your gas consumption jumps to ONLY 1 CFM, give yourself only 1 minute to deal with the situation, you just sucked 4 cubic feet, for easy math you come up to 70' and do your one minute deepstop, that's 2 mintues and we'll round down to 3 ata so thats 6 more cubic feet, 1 minute travel to 40 feet, (round down even more) 2 cuft, 3 minute safety stop another 4 cuft or so, thats 16 cubic feet, dont forget you want to leave at least 500 psi to make up for SPG variances. What if your buddy is up the same creek, then you double your gas and you're at 32 cubic feet.