My nearly empty tin of paint stripper had been bulging, which was scary enough...I'd open it and a rush of air would shoot out.
But then it started doing this (pics).
It was when it started whistling tonight (while I was using it - decanting a little into another pot then resealing) that I thought I'd better just crack it open for good and get the dregs out.
And if you've never seen it...this is something similar happening instantaneously to a REINFORCED fuel tanker!!!