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Hi folks I just wanted to through out some thoughts for discussion about gas managment on deepish dives. The senerio Sydney,Australia non-penetration wreck diving, the wrecks are not that big so there is not really an out and back, just a muck around near the anchor. The depths are from 130fsw to 180fsw. Dived usings independant twins and sometimes a pony of deco gas (nitrox something depending on schedule). The book says to use the thirds rule, 1 out , 1 back , 1 in reserve, but as I pointed out earlier there is no out and back. Is this only your bottom gas ie the last third is reserve and not what you deco on? Is it nessacary to leave a third in a non-physical overhead environment allowing for the glass cieling of deco.Any problems and up I go to deco on my lift bag. My thoughts... If diving without pony, leave enough to decompress on in one tank (or 90 BAR whichever is more) and twice that amount in the other. This should allow me to decompress even if I lose a tank and also have enough to decompress two divers if required (3 actually but that would be to empty). The only senario that I can see a problem with is for my buddy to lose all gas and for me to have lost the tank with the *2 deco in it, but this means that we have had 3 complete and seperate system failures. If diving with a pony I would ommitt the *2 in the second tank and drink this down to the single deco requirments.(allowing for the extended time to deco on air instead of nitox etc). The question is "Is this a safe gas managment practice or not?" By how much should I PAD my gas requirments when I calculate, by 1/3 by a 1/2 or what? Thanks in advance Terry -- ******************************************************************** Terry McCracken GEC ALSTHOM Information Technology Software Support Engineer Ph: 61 2 415 0509 terrym@ns*.co*.au* Fax: 61 2 417 8635
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