[PATCH] MOD of oxygen at pO2 of 1.6 is 20ft

Dirk Hohndel dirk at hohndel.org
Mon Jul 6 06:42:26 PDT 2015

On Mon, Jul 06, 2015 at 09:56:20AM -0300, Rodrigo Severo wrote:
> On Mon, Jul 6, 2015 at 4:24 AM, Henrik Brautaset Aronsen
> <subsurface at henrik.synth.no> wrote:
> >
> > On Sun, Jul 5, 2015 at 11:03 PM, Rick Walsh <rickmwalsh at gmail.com> wrote:
> >>
> >> Serious question: does anyone switch to 50% at 22m?
> >
> >
> > For tank MOD markings around me usually round to the nearest 3 (meters).  So 21 meters (not 22) for 50% and 6 meters (not 5) for o2.  Etc.  Also to the nearest 10ft.
> I dive metric, my stops are all multiple of 3 m and my tanks have the
> real MODs, not rounded ones, as I understand MODs as maximum operation
> depth, not mandatory other-gas depth ;) But obviously I understand
> that having the MOD equal to some deco stop might seems less
> confusing.

Thanks for the data points.

> Truncating sounds more conservative but actually I bet that if your
> dive plan gets unsafe because of half a meter on a deco stop or worst
> half a foot you have other problems not rounding related so rounding
> seems to me as the right thing to do.

I completely agree. And as I said, the important reason to switch to
rounding was to get Oxygen at 20ft - I think we can all agree that that's
the common practice. I don't know of any tech diver who thinks that they
can't switch to O₂ at 20ft.


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