PASS device
（重定向自Personal Alert Safety System）
A PASS device (Personal Alert Safety System) also known as a distress signal unit (DSU) or ADSU (Automatic Distress Signal Unit), is a personal safety device used primarily by firefighters entering a hazardous (IDLH) environment such as a burning building. The PASS device sounds a loud (95 decibel) audible alert to notify others in the area that the firefighter is in distress. On a fireground, the sound of an activated PASS device indicates a true emergency and results in an immediate response to rescue the firefighter(s) in distress. In the United States, the National Fire Protection Association sets standards for PASS devices in NFPA 1982.