Well, Ronny, I advise you read this page!
*sighs* listen up idiots
basically, a fire alarm is linked up to a smoke detector, and a smoke detector works by passing alpha radiation across a small space of air. a long as the recieving part of the radiation stays at a constant level, then the air is clean, and therefore there is no smoke. but if slightly more dense gases, such as SMOKE or in this case, your stink bomb, cover this up, then the alarm will be triggered.
Simple as 馃槃