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PASS Sound Muffle Tests Using A Structural Firefighter Protective Ensemble Method



James R. Lawson


Firefighters and other emergency responders often work in adverse environments. The operating environments can be very noisy. Personal Alert Safety Systems (PASS) devices are safety systems that emit an audible alarm signal when an emergency responder stops moving. This alarm signal serves as a means for others to rapidly locate a responder who may be injured and down. The 2007 edition of NFPA 1982, Standard on Personal Alert Safety Systems (PASS) established a means to evaluate the muffling (attenuation) of sound level from a PASS device worn by an emergency responder who is down on the floor. The standard prescribes five different test positions that are assumed when measuring sound level attenuation from a firefighter, fully dressed in their NFPA 1971 fire fighting ensemble, while wearing a PASS device that is in full alarm. NIST tested five different pass devices in an open laboratory room environment to determine relative signal level degradation for each device. Results from the tests were mixed with sound level losses ranging from 8.6 percent dBA to 19.2 percent dBA. These signal level losses are associated with the type of device, direction of measurement from the PASS device, and losses resulting from the firefighter s body blocking the sound path.
Technical Note (NIST TN) - 1641
Report Number


alarms, emergency responder, firefighter, safety, sound level, standards, test


Lawson, J. (2009), PASS Sound Muffle Tests Using A Structural Firefighter Protective Ensemble Method, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed June 15, 2024)


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Created July 7, 2009, Updated February 19, 2017