This comes up every so often so here is some info on smoke units and fluid.
http://www.trainweb.org/girr/tips/tips3/smoke_tips.html
http://www.kato-unitrack.co.uk/seuthe-smoke-units-9280-0.html
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.