I have no trouble getting to sleep at night (takes five-ten minutes to fall asleep), but whenever I stay over at my friend's place, it takes anywhere from half an hour to an hour to fall asleep, I wake up after two or three hours, and can't seem to fall back asleep (and end up tossing around for another few hours). I am physically tired, but my brain just seems very alert, as if it isn't tired and doesn't want to shut off.

My friend's a smoker (I'm not), so the room has a distinct smell of smoke and nicotine. Since nicotine is a stimulant, could it be that the trace amounts floating around in the air are keeping my brain constantly activated, preventing me from sleeping? Also, is there anything I could do to make myself sleep better in such a situation? Thanks!