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A PPO2 of 1.4 is what is recommended on the bottom by all of the training agencies I am aware of. SO, a PPO2 of 1.47 would be a tad hot.
ANDI recommends 1.45, or at least it used to. That's a little closer.
The 1.4 is rather arbitrary, just as PADI's 60' maximum depth for open water divers is rather arbitrary.
And what other training agencies are you aware of? I just checked my TDI "A Diver's Guide to Advanced Nitrox Diving" (2001 rev 2) and found the following:
"Typically we will use 1.6 ATA for any 'maximum' exposures of oxygen, although some divers may reduce that depending on the diving conditions. . . . Remember back to your Nitrox course, it is YOU who determines what oxygen exposure you want for the dive. In many cases, this will be the 1.6 ATA as previously indicated, however, some divers choose 1.5 ATA or even 1.4 ATA as the maximum value for their particular dive." (p. 18)
"At an oxygen exposure of 1.6 ATA, the diver is limited to a 45-minute single exposure." (p. 35)
There are far more liberal guides out there, to be sure. In Weinke's Technical Diving in Depth, for instance, Table 7 on p. 92 gives the Oxygen Exception Exposure Time Limits, showing a 75 min single exposure limit for 1.6. It also gives 75 min at 1.7, 60 min at 1.8, 45 min at 1.9, and 30 min at 2.0. The latter used to be considered the standard MOD until we got too dang conservative and started using 1.6. Now it's 1.4. By tomorrow it will probably be 1.0, with really conservative folks telling you to not use nitrox below the surface or you'll certainly die. And then we'll have come full circle.
GUE is 1.4 max, 1.2 average on shallow dives; 1.0 (or lower...) for deep stuff. We're a bunch of pu$$ies, though (and don't mind a bit of extra deco vs. the tox risk and less efficient deco).
NAUI is 1.4 with 1.6 for contingencies. Gotta draw the line somewhere and based on this question, not sure how I am the one over analyzing.
Drawing the line somewhere is one thing, implying that the diver had more important issues to worry about besides an octopus squeezing his carotid artery simply because he barely exceeded 1.4 for 15 min isn't overanalyzing, it's just dead wrong.
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Originally Posted by SeaCobra
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