Quest for Clarity
Why it’s important to understand MNS intelligibility
By Wayne Moore
THE PROLIFERATION OF installed mass notification systems (MNS) and the building code requirements for voice fire alarm systems in occupancies such as new K–12 schools have raised ongoing questions regarding the intelligibility requirements of the 2016 edition of NFPA 72®, National Fire Alarm and Signaling Code. The code specifies voice intelligibility for all voice systems, but it does not require the evaluation of intelligibility “through quantitative measurements.” The code does not say why measurements are not required, but an understanding of the factors that affect intelligibility will give users and enforcers of the code a better understanding of the technical committee’s intent.
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