On Fri, 21 Jun 2013 21:20:32 -0400, (PeteCresswell) wrote:

I guess I should pour a cupful of gas into the suspect one, seal it,
leave it in the sun for a few hours, and then crack to cap to see of
there's an audible sound of vapor release.

When I had called the CARB 800-242-4450, I spoke to Angus 916-445-4686
about gasoline cans; he told me they *weigh* them after a period of
something like 120 days (I had posted at the time the exact spec)
and they can't lose anything. There is also an accelerated test.

Interestingly, he said there is a spec for a can with a second opening,
but, that none of the six companies approved for California sales has
ever submitted a can for certification that has that second opening
(i.e., a vent).