There are several different kinds of smoke detectors (I was dragged into a seminar once..) As I recall, most house hold smoke detectors operate off of a light and a sensor. Think of a T - the sensor is at the bottom point of the T, the light is on the top left, and the top of the T is a channel for air to circulate through. As long as the sensor can see the light, all is good. As soon as there is too much "smoke" blocking the sensor from seeing the light, the alarm sounds. This is just one of several smoke alarm technologies, but it's the most common for house hold smoke alarms - I'm not sure what's in the bathroom at the college (or the one the other poster claimed to have set off). Point being, I don't think the content of the vapor (carbon _oxide) matters. I think it is more the density of the molecules which prevents light from getting to the sensor.
Maybe if you really put your mind to it you could fog up the smoke alarm enough to cause it to go off... That being said, I have a smoke alarm in my office (about 10x10 room) and I'm vaping all day and have not had any problems. Also, the vapor seems to want to sink to the floor more than go up toward the roof. I'm not producing large clouds (yet) but if there was going to be a problem, I think I would have came across it now.