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PASS Sound Muffle Tests Using A Structural Firefighter Protective Ensemble Method.

pdf icon PASS Sound Muffle Tests Using A Structural Firefighter Protective Ensemble Method. (432 K)
Lawson, J. R.

NIST Technical Note 1641; NIST TN 1641; 28 p. July 2009.


protective equipment; fire fighters; first responders; fire alarm systems; safety; noise (sound); NFPA 1982; NFPA 1971; fire fighting; attenuation; fire fighting equipment; instruments; fire tests


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 or incapacitated. The 2007 edition of National Fire Protection Association, 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 room environment to determine relative signal level attenuation for each device. These tests demonstrate sound level losses ranging from approximately 9% dBA to 19% dBA. These signal losses are associated with the type of device, direction of measurement relative to the orientation of the PASS device, and attenuation from the firefighter's body obstructing the sound path. This report also contains background sound level measurements with dBA measurements from fire fighting apparatus and power tools that are commonly used on the fireground.