Time adjustment for deco stop on 100% O2 vs. air (21%)

[Karl_H]

Roughly 1/2. 14 minutes on Air, figure 7 minutes on O2. But it would be stupid (possibly deadly) to not verify this with tables.
Who's your AN/DP & Cave Instructor?

I guess this would work but is very conservative, not that this is a bad thing! A (very) simplified approach is just to look at the N2 pressure gradients, for air you'd have about 80% nitrogen at 1.6 ATA so a PPN2 of around 1.3 at 20'/6m vs a PPN2 of zero for O2. The water pressure keeping saturated gas in your tissues should be 1.6 ATA at 20'/6m - this gives a pressure gradient of 0.3 for air vs 1.6 for O2 - a BIG difference, there a lot more to it that just one pressure gradient though.

It's seriously worth buying V-Planner though, I still rate it as the best planning software out there. Most technical computers (including Shearwater) use a GF model - no big deal for CCR but for open circuit dives I'd recommend VPM (i.e. V-Planner) as it works well with adjusted stops around gas switches to get the most out of the O2 window effect on the nitrogen pressure gradient.

If you have the V-Planner software and go for the Liquivision X1 you'll have the same software for both pre-planning and live during the dive on your computer.

---------- Post Merged at 06:22 PM ---------- Previous Post was at 09:24 AM ----------

Most technical computers (including Shearwater) use a GF model - no big deal for CCR but for open circuit dives I'd recommend VPM (i.e. V-Planner) as it works well with adjusted stops around gas switches to get the most out of the O2 window effect on the nitrogen pressure gradient.

Self correction here - you can also get a VPM upgrade for the Predator and Petrel - looks like I'm way out of date on that one, I still like the X1 though - I have both a Predator and a X1 so have no bought-in allegiance to one particular brand!

Karl

 

[Divin'Papaw]

DH - you can also stick your advice "you know where." I did not ask anyone's opinion what I should spend my money on.

I am waiting on the Dive Rite Workbench software, having bought a DR Nitek Q, and evaluating V-P, which I most likely will purchase. I ask questions to acquire information and to find out what others do. Any conclusion I come to and folliow will be vetted somewhat scientifically (my profession) to my satisfaction. I have enough education (PhD, etc.) to do research and can write my own software if neccessary. Yours and other's self righteous, "snarky" comments only show how limited your knowledge really is.

If you don't want a snarky answer, than don't ask how planning software would calculate a profile using O2 simply because you haven't officially purchased it and therefore can't actually calculate the desired profile. Asking questions about the profile it generates and why is one thing, but trying to extrapolate a profile using O2 based upon one using 50% simply because you haven't yet bought the software deserves a snarky response. Being a brilliant PhD, I'd expect you can easily find the $85.

Good luck with your training. If you don't want snarky responses, you might want to provide more context next time.