dealing with unused tanks

[Linus Torvalds]

On Sun, Dec 30, 2012 at 12:52 PM, Jef Driesen <jefdriesen at telenet.be> wrote:
>
> Are there any devices that allow switching to inactive gasmixes during the
> dive. That would be very counter intuitive. If the answer is yes, then
> what's the purpose of marking a gas as inactive?

One obvious purpose for marking it inactive would mean that the dive
computer wouldn't use it for any future deco calculations (ie the
"minimum time to surface" number).

For example, if you have a bail-out bottle with 50% O2 or something
that you do *NOT* want to use except in emergencies, you may well want
to list it in the dive computer (in case you have to use it you can
switch to it and get deco info using that knowledge), but you'd want
to mark it as "inactive" to make sure that the dive computer doesn't
think you're going to use it for your deco stop.

                   Linus