Originally Posted by zelda_pinwheel
i have a friend whose parents had an alarm system like that, once a spider made a nest in one of the sensors and it went off in the middle of the night and woke everyone up. (further proof that spiders are evil). (actually, once i was spending the weekend there and didn't know about the alarm, and got up in the middle of the night to get a drink of water, and his mother heard me in the kitchen and came running down the stairs to turn off the alarm before it went off and scared me half to death).
We had something like that too, when I still lived at home. We couldn't figure out why the alarm went off in the middle of the night, sometimes. Not always. So, my parents called the maintenance guys. And they found out an earwig had crawled inside the detector. And every now and again he would try to climb out, triggering the movement alarm
As answer to the original question: do all rooms have an alarm in them, or is it only in certain rooms and hallways?