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Yes, I recall some medical students use to mess around with it, but it was only really student types. I don't remember seeing car parks littered with cannisters until maybe 12 months ago. I think I was wrong to think it was just something that Pakistani heritage youths do- it is round here, all in cars, doing it openly and leaving a mess- but Retrocop's example was a different community and the cannisters seem to be in most towns now so I suppose it must be white working class and middle class too, in fact all groups.
I'm going to fill my recycling bin today- I'm fed up of seeing them littering the streets and car parks