Firefighters, by the nature of their job, find themselves in life-threatening situations regularly. They carry a device called a Personal Alert Safety System, or PASS, just in case. The PASS is a motion-triggered alarm, attached to the harness that keeps their oxygen tank on. If the firefighter, and thus the PASS, doesn't move for 5 seconds straight, the alarm begins beeping loudly. If it's not addressed, it soon goes into alarm mode, screeching at about 95 decibels to alert other firefighters in the area. That's very loud, but firefighters report that it doesn't really work well, for the odd reason that they can't hear it in a burning building.