Most recently I've had trouble with imagined smells, of which was a thick stench of cigarette smoke that wasn't there. Very upsetting because I started having real symptoms of smoke inhalation- head ache, scratchy throat. etc. I was trying to pinpoint the source at first because I do have a neighbor who on occasion chain smokes and the smell drifts into my apartment. I went outside and the smell wasn't there. It wasn't in my bedroom. Just right in the middle of my living room. Usually when this happens it only last a few minutes, this was over an hour, and so I finally went for a walk. I had to leave my apartment for fresh air and I knew I was hallucinating because the small followed me, though not as strong and it eventually went away.