Fog in an A320 cabin
A while ago I was down the back of an A320. It was a bright but slightly humid early morning departure. During the take-off roll a fog appeared at vents at the top of the window panel (i.e. just below the overhead bins). The fog lasted for about 6 inches before dissipating quickly. It stopped being produced after the aircraft was passing 2000ft or so without any noticable change of engine power at the time.
I presumed this was a result of the VAC system combined with the humidity inside and outside the cabin. Is this right, or maybe there was some fault? I've not seen it again since - and I've been on far too many early morning A320 flights for my liking lately - is it common?
It was very pretty.