I'm choking on cigarette smoke. I wake up look around, sniff, and realize--there's no smoke in here. I'm the only one in this room, and I'm not smoking. I fall asleep, and I choke on more cigarette smoke--it's in my lungs and I can smell it. I choke and wake up, choke and wake up, choke and wake up several more times. Finally I convince myself--There's NO smoke, and I drift off for the rest of the night.