divelist.c: gasmix-default translation

Dirk Hohndel dirk at hohndel.org
Fri Oct 19 07:31:51 PDT 2012

"Lubomir I. Ivanov" <neolit123 at gmail.com> writes:

> divelist.c:nitrox_data_func():
> if the gas mix values for a dive are zero for O2 and He we show "air",
> which isn't translated and perhaps it should.
> i'm not an expert, but should "air" be used to describe a more neutral
> state when the only two gases we are interested in a proportion are
> both missing?
> http://en.wikipedia.org/wiki/Diving_cylinder
> "These cylinders typically contain (atmospheric) breathing air, or an
> oxygen-enriched air mix:"
> i can also see 72% N used here for "nitrox":
> http://en.wikipedia.org/wiki/Nitrox
> but we are only mixing O2 and He in nitrox_data_func()...hm.
> forgive my ignorant intrusion...

Hehe... the non-diver at work. :-)

This is totally illogical, but it's how most divers think of their
breathing gas:

20.9% O2, 78.1% N2 and small amount of random other gases (ok, not
random, but we usually ignore them). That's air. And even though it DOES
have a distinct O2 amount, we don't list this is EAN20.9 or 20.9%
Nitrox, we list it as air.

Anything with a higher O2 content (and accordingly, lower N2 content) is
listed by its O2 content: EAN32 or 32% Nitrox is very common (and
apparently the only Nitrox level available / legal in Japan). But you
see much higher concentration in deco gases - I've done EAN70 deco on
one dive.

And then, if you want to go deeper than about 50m (and yes, I know,
crazy people go WAY deeper than that on air, but let's be real), then
you want to REDUCE your O2 content (as it gets toxic at partial
pressures above 1.4/1.6/2.0/whatever number you want to believe).
AND you want to reduce the N2 content as that causes a phenomenon called
Narcosis above a certain level. So you add He2 to the mix. And once
again, all we list is the O2 and He2 - the rest being basically N2 is
simply assumed.

Does this all make more sense now?


PS: and yes, all this said, we SHOULD translate air into other languages.

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