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Rodney there is a quiet a difference in the o2 clock at 30 feet on EAN 80 po 2 of 1.53 in sea water at 30 feet ( the tables actually call for on the accelerated tables EAN 75 and on the run time tables for air and EANx EAN 78, the trimix tables call for EAN 75 also). As you know o2 at exactly 20 feet/6meters is 1.61 ata and it runs the clock up fast. At the same time their is very little difference in the runtime of a dive. I agree we could make tables that started using 02 at a more shallow depth 5 meters would work well and it would simply mean a slight adjustment on the 9 meter stop so that it would become a fraction longer. Prehaps in the future we will look at that. For the time being we are quiet happy with the tables we are using and the deco clock is considerably lowere than when using 02. you have deco soft ware so I suggest you run some comparisions. Tom You wrote: > >> >> Jess >> You will most likely be much safer using less than 1.6 ATA po 2 at >> deco. The reason IANTD in 1991 started encouragement of EAN 80 was to >> reduce the deco po2. We did not do this because we thought there may be >> a problem, we did it because several divers did have problems using o2 >> at 20 feet. As you know there have been o2 hits on o2 at 20 foot. To my >> knowlege no o2 hits have taken place on EAN 80. I do not know of anyone >> getting bent using EAN 80 and in my own plus my students and numerous >> other IANTD instructors and students dives alone we can document >> thousands of dives using EAN 80 for deco. >> >> In caves it is not as much of a problem as the 20 foot stop is usually >> stable. In open water divers tend to stay slightly deeper than 20 feet >> and if they are as deep as 23 it is 1.7 po2. >> >> On all models that I'm aware of there is little difference in deco time >> but a lot of difference in the o2 loading between EAN 80 and o2. I have >> no doubt that from a deco standpoint there are advantages to pure o2 >> and in mixing it certainly is much simplier, but do the advantages >> outweigh the risk. For me they do not. >> >> George once posted that he had started putting a little air on top of >> his o2 due to tox risk. I know in personal communication that this >> followed a dive where he experienced some symptoms of o2 tox. I do not >> know if he is still putting air on top of his o2 or not. From his >> response to you I guess he has gone back to pure o2. >> >> Tom Mount > >Tom, you state that you started using ntx80 to >reduce the risk of 02 tox, but while you reduced the >02, you increased the depth, which defeats the >purpose. > >You state that in the ocean, you can go 3ft deeper >than the stop on ntx80 and still not exeed 1.6. >The same can also be said for 02 at 5mtrs, which >has all the advantages of pure 02, and all the safety >of ntx80. All you need is tables that give a >5mtr stop. > >Either that or use the ntx80 in place of 02, at the 6 >and 3 stops only. I know this is not what people >want to hear. > >And anyone can get pure 02, no need to mix gas >or do 4 courses. > >Rod Nairne. >-- >Send mail for the `techdiver' mailing list to `techdiver@terra.net'. >Send subscription/archive requests to `techdiver-request@terra.net'. >
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