I’ve had to use these before, when I lived in a dormitory that had frequent false fire alarms. The fire exit stairs took us to a series of one-way locking doors, ending with a “Do not exit, alarm will sound” door. At that point, even if we felt like it might be a false alarm, we had no choice but to go through the door. The first several times, it set off a weak alarm, but did not appear to be wired into anything else in the building. After a few times, it stopped going off, I assume because its battery died. It’s nobody’s job to replace those batteries, so they stay dead.