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Hal,

>As to the O2 clock, there's no problem.  The O2PP for the first dive
>1.107ATA with a single exposure allowed of 3.5hrs.  This was just a 20 min
>dive.  The deco was less than 10 minutes on 80% O2 at 10fsw for an O2PP of
>1.3ATA with a total of 3hrs. max allowable.  The dives were then seperated
>by over 2 hrs on air at the surface.  The last dive was an O2PP of 1.51ATA
>for 20 minutes with 2hrs allowed.  So each segment was well within limits
>and in total the limits were not exceeded. But not a bad question to ask.


I am not sure what CNS O2 limits you are using, but if your ppO2 for
the second dive was 1.5+ ATA, then you should use 1.6 as your limiting
value, and this (according to NOAA) has a single exposure limit max of
45 minutes, with the maximum of 2.5 hours allowed in any 24 hour period.
As I read the NOAA manual, their single exposure limits apply to
each anmd every single exposure made during a 24 hour period, and the sum
of those exposures are not to exceed the 24 hour limit.

So, how are you calculating your CNS clock?  Based on the single exposure
limits, or only on the 24 hour limits?  Are you calculating recovery between
dives?  If so, how?

I am not thowing stones, but have noticed a trend for nitrox divers to
ignore the single dive limits (because they are very restricting) and
embrace the 24 hour limits instead.

John

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