Mandatory safety stop vs. deco

[Miika Turkia]

On Mon, Sep 9, 2013 at 6:11 PM, Dirk Hohndel <dirk at hohndel.org> wrote:

> On Mon, 2013-09-09 at 18:07 +0300, Miika Turkia wrote:
> > I have one dive that according to libdivecomputer/subsurface goes into
> > deco. However, the dive was actually a non-deco dive with a bit of
> > extra excitement caused by heavy up current (roughly from 13 to 8
> > meters in 10 seconds). Due to the rapid ascent, Suunto gave a
> > mandatory safety stop that is currently considered as going into deco.
>
> That's almost a philosophical question...
>
> If a safety stop is "mandatory", how is it different from a "deco stop"?
>

To my understanding, when one is in deco, some tissues have absorbed too
much nitrogen to safely ascent to surface. In  case of rapid ascent such
over-saturation has not happened. (correct me if I am wrong)


> > I want to throw in a question whether this should be considered deco
> > or not. I guess one can argue either way but nevertheless it was a
> > surprise to see the deco marking in subsurface.
> >
> >
> > libdivecomputer/src/suunto_d9_parser.c:
> > case 0x01: // Mandatory Safety Stop - odd concept; model as deco stop
> >        sample.event.type = SAMPLE_EVENT_SAFETYSTOP_MANDATORY;
> >        if (type & 0x80)
> >               in_deco &= ~DECOSTOP;
> >        else
> >               in_deco |= DECOSTOP;
> >        break;
>
> So yes - this was a conscious decision that I made when implementing
> this. If people feel strongly about it, it's of course open to
> discussion, but as I mentioned above, I find this a subtle distinction
> without a difference...
>

It was a surprise that warranted a bit of digging to find out what is going
on, why the deco. This also seems to depend on the Suunto model whether you
get mandatory safety stop or not. My Stinger didn't mind the ascent...

miika
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