David Strike wrote:

> At one time, ( and I still do!<bwg>), I accepted that a PPO2 of 2 ata's
was
> perfectly acceptable - and safe! :-)

At one time, before I knew what a PPO2 was, so did I.  I can clearly recall
believing that a 100% O2 rebreather was safe at 33 feet but would promptly
kill you at any greater depth.  When I finally got around to learning more
about higher PPO2 gas and its use for diving, the industry standard had just
shifted from 1.6 to 1.4.  My personal belief is that 1.6 was a conservative
adjustment to 2.0 and that 1.4 is a further adjustment because 1.6 didn't
work for everybody.  Then there is the issue of time . . .

My standard, the one I dive by, is to plan for 1.4 or less, accept 1.6 if
there's a good reason to exceed my planned PPO2 and stop there unless
there's enough reason for me to do so to offset a potential risk to my own
life, a pretty high standard.  These limits may be more conservative than
what may still be safe, but they work for me, which is as good a reason for
them as I can come up with.

Lee