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Hi; I have some questions about Decompression. I have a favorite wreck that I dive a lot in the St. Lawrence river near Brockville, ontario, canada. Its called the J.B. King and it is a large ship that was carrying explosives when it was struck by lightening. The wreck is only in 150 feet, and my deco is usually in the 40 minutes to an hour range. There is a local TDI instructor here in Ottawa (very good reputation) who has recently started decompressing on either surface suplied O2 or 50/50 nitrox. He has also stated that decompression times longer than about 20 minutes on air are unsafe. I have seen studies that say doing deco on EAN can decrease the incidence of DCS by 2-3 times, HOWEVER, I can't find any studies that show what the rate of DCS is on long deco on regular Air. Ok, now I guess I should put on my flame retardent dry suit before I make this next comment. To decompress on pure O2 or on Nitrox is going to cost my wife and I at least 20 bucks a dive. This can amount to some substantial bucks. What I want to know is: "Is air deco really 'unsafe', or is it just less safe." Does anyone have numbers about DCS hit rates with deco on different gases? I'm really looking for concrete numbers here, not speculation. Item #2 ------- There is another wreck I want to dive on called the "Jodry". Its a 600 foot long laker that went down in about 200 feet of water. I am pretty sure I can deal with the narcosis, but I wonder what the chances of toxing are if I do this on air. (I realize that the P02 on this is only 1.45 or so, but it may be chilly and there might be enough of a current that I have to work a little bit) The water temp in the St. lawrence hits a high of about 70 and I probably won't try this wreck when the temp is below about 60. The current can vary between 1-2 knots. -- Regards, Andy W. Barclay. andy@le*.ca* UNIX Instructor Team Leader Decisions of the judges will be final unless shouted down by a really overwhelming majority of the crowd present. Abusive and obscene language may not be used by contestants when addressing members of the judging panel, or, conversly, by members of the judging panel when addressing contestants. (Unless struck by a boomerang). --Mudgeeraba Creek Emu-Riding and Boomerang-Throwing Assoc.
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