David Strike wrote:

> I remember that about twelve or so years ago, one of the - then - few dive
> stores to offer mixed gas fills (in Oz), made a point of filling cylinders
> the day prior to use to allow time for proper diffusion to take place.
(He
> even used to roll the cylinders around and I wouldn't mind betting, had he
> been stronger, that he'd have picked them up and waggled them vigorously
> like a cocktail shaker!  :-)

I've seen this done even more recently than that, say in the last 12 months.
Personally, I always figured that the introduction of air into a tank full
of oxygen is likely to do a fair job of stirring things up.  Still, I
generally check my mix shortly before using it rather than immediately after
a fill, or more correctly, I check it after the fill and again before use.
I've yet to get significantly different results.

Lee