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I'm going to try this one more time and then move on to other things. I originally responded to two focused points and I believe they still stand. Yes, ANDI teaches 1.6 ata is the maximum recommended PO2 exposure, and we do it in good company. NO, ANDI does not teach, nor has anyone provided a citation where using a 50/50 mix at 130 feet is suggested. You fight over the rest. Regarding bailout mixes, Frank pointed out that: "ANDI recommends the PO2 of a bailout mix to never exceed 2.0 ata." Yes. As in all dive planning, if you plan, expect, or can (reasonably - you define what it means) find yourself in the types of situations he described, of course adjust accordingly. They are not requirements. Like the 1.6, 2.0 is an upper limit. There are "limits" in all aspects of life. If they are not appropriate to the situation, back away from them. . "50/50 as a bailout gas has an MOD of 100 fsw". (Thanks, Frank for independently pointing this out.) Yes. There is a difference, and hence a dive planning difference between the purpose of a backup gas supply and a bailout-and/or-deco supply. Don't many divers sling oxygen bottles (or 80/20) throughout an entire dive just to use for deco? While it may be a waste of energy to carry it, no one advocates using that gas as a bottom backup gas. If you want your bailout gas to serve double duty as a backup gas, of course you must anticipate your ability to perform an immediate ascent, if it becomes necessary. Should you determine you might not be able to, then adjust your mix accordingly. (Remember, our CSU and LSU divers are no decompression, no overhead environment...) Diving includes an assumption of risk. A diver decides how much risk he is comfortable with. He/she then manages it by properly planning his dives within the limits of his training, experience, recency and equipment. Dive planning is done with the eyes open. Appropriate planning takes into account the circumstances and contingencies one expects to encounter and tempers it with a dose of reasonability. If the limits are contraindicated by the expected dive conditions, don't push the limits. No one has suggested otherwise. ----------------------------------------------- Stuart Masch, Chief Operating Officer American Nitrox Divers International
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