Quote Originally Posted by addexdiver View Post
I ran several nitrox blends from 21 to 32% through decoplanner for a 3 hour dive at 100 feet with a single deco gas at 100% O2. The O2 toxity clock stayed under 100% during the dive for all mixes (of course dropping for lower PO2 mixes), but in all cases exceeded 100% during deco with the final O2 clock upon surfacing being virtually the same for all bottom mixes. The reason for this was that dives on lower PO2 ran longer deco at the higher PO2.

Bob
We played with basically the same thing today and it is true that at best you only save a few percent on the CNS clock if you back off on the PO2 - at least with the more conservative models in general use today.

On the other hand, there are advantages to having a lower PO2 on the higher work portions of the dive, and on deco, you can at least add in some air breaks.

It does however also creates a potential argument for pumping 80% as a deco gas rather than 100%.