Same gas cylinders

Davide DB dbdavide at
Mon Jul 14 16:08:05 PDT 2014

2014-07-14 21:27 GMT+02:00 Anton Lundin <glance at>:

> On 14 July, 2014 - Davide DB wrote:
> > I sadly discovered this
> >
> >
> >
> > Any news? User comments describe perfectly the problem.
> >
> Still thinking about it. Haven't found any good design for it yet.
> The problem is that we currently model our gas switches after how most
> dc's handle them, you switch to a gas, not a cylinder. There are quite
> allot of assumptions in the code that it works that way, so reworking
> this is a non-trivial task.

I understand.
Looking at one of my oxygen gas change event I found:

*<event time="119:26 min" name="gaschange" value="100" type="25"/>*

So I guess it refers to the gas via the oxygen fraction. Humm...

In an advanced tech/cave dives I easily have one of these scenario:

Gas switches between several identical stage bottles with the same mix.
Gas switch from a bottom stage and back gas.
Gas switch from my back gas to a stage bottle during descent in a PSCR dive
(even in an arbitrary point in a cave dive).

2nd & 3rd scenarios switch between different bottle type. 1st scenario
switches between same bottle type so cylinder type is not enough.
Is it really so difficult having something like bottle id in the cylinder
record and then referring later to it by id without breaking other code?

Enhancement ticket for 5.0 :)

> If anyone can come up with a good model that doesn't break things too
> badly and implement it, sure, but until then its a wish for the future.
> I've managed to trick subsurface into reading the all my dives with
> such gases the right way, its involves some trickery, but its doable,
> and not for the faint-hearted.

By the moment the only workaround I found is having a slightly different
mix in every stage bottle.


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