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PASS alarm signals can fail at high temperatures

Exposure to high-temperature environments may cause the loudness of PASS alarm signals to be reduced

December 13, 2007 
By Fire Fighting in Canada

Exposure to high-temperature environments may cause the loudness of PASS alarm signals to be reduced, the NFPA reported in early December.  This reduction in loudness could cause the alarm signal to become indistinguishable from background noise at the incident scene. This problem was brought to the attention of the NFPA Technical Committee on Electronic Safety Equipment by the National Institute for Occupational Safety and Health’s (NIOSH) Fire Fighter Fatality Investigation and Prevention Program. 

NIOSH reported that during the investigation of four firefighter fatalities that occurred from 2001 to 2004, the PASS alarms were not heard or were barely audible. The PASS had been certified as compliant to NFPA 1982, Standard on Personal Alert Safety Systems (PASS), 1998 Edition, and involved both stand-alone PASS and SCBA-integrated PASS. 

Initial laboratory testing of PASS by the National Institute for Standards and Technology has shown this sound reduction may begin to occur at temperatures as low as 300-degrees F (150 C) and could affect all PASS devices.  Additional work is required to better characterize the thermal conditions (temperatures and exposure durations) that contribute to alarm signal degradation.

While the NFPA committee has been working to develop appropriate revisions to NFPA 1982 to address this issue, adequate solutions have not yet been presented.  The committee, in co-operation with NIOSH and NIST, will continue to study the issue and will incorporate revisions as solutions are developed.


PASS has always been a “last resort call for help” for personnel who are unable to otherwise notify others that they are in distress.  Firefighters should continue to activate and wear PASS whenever in hazardous areas of any incident, but should also be aware that high temperatures could cause degradation of the alarm signal. Incident command should continue to apply all personnel accountability measures at all incidents to assure the safe entrance and exit of personnel.

Emergency services organizations and personnel should report any PASS malfunctions and other problems with PASS directly to both the certification organization whose certification mark appears on the PASS, and to NIOSH. Contact NIOSH–NPPTL at :

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