I still live at my parents, and my room has a smoke detector. It's a pretty small room, too. Only about four people can fit in it comfortably. We toke it up in here so bad sometimes that the room is hazy. It never sets off the smoke alarm, though. We were high one night and decided to try and set it off, so we each took a big hit and blew on it at the same time. No go. After that we thought it might be busted, so I lit a piece of paper and held it about three feet below and it went off instantly. Maybe pot smoke isn't hot enough to set one off? Maybe the bong water cooled it enough? We've used pipes and joints too... maybe stoners invented the smoke detector!