SAC and Gas Consumed Calculation

Dirk Hohndel dirk at
Tue Feb 11 14:00:27 UTC 2014

On Tue, 2014-02-11 at 12:46 -0800, Linus Torvalds wrote:
> On Tue, Feb 11, 2014 at 12:18 PM, Rick Walsh <rickmwalsh at> wrote:
> >
> > Also helps explain why I've found consumption, measured the
> > easy/wrong/padi/my way appears better when using aluminium tanks filled to
> > 200-210 bar (aka ~3000psi) as opposed to steel tanks at 230-240 bar. I
> > thought it was all down to being more relaxed and breathing slower in easy
> > diving conditions in warm tropical waters, where AL80s are the norm.
> I'm sure it's a combination of the two. In fact, I'd expect the effect
> of "easy diving in warm tropical waters" to be much more.
> I certainly notice that my SAC rate in nice diving in warm waters
> tends to hover around 12l, while the technical diving during my trimix
> course was almost double. Oops.

First time we had twins on our backs we pointed out to the instructor
that at twice the SAC rate the twins don't really offer a lot more TIME
under water :-)

By now my SAC rate with twins in cold water is only about 10-15% higher
than in with an AL80 in warm water...
> > Can a statement that gas incompressibility at high pressure is considered
> > when calculating gas consumption be added to the manual so other
> > ill-informed divers, like me, don't get confused?
> It might be a good idea. It would be possibly even better to have some
> kind of "help when hovering over values" thing.

Great idea.

Willem, can you add this to the manual?

Tomaz, could we do this in the dive list?


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