Audible Notification Requirements
Chapter 18 of NFPA 72 governs the design and installation of notification appliances, the components responsible for alerting building occupants to a fire or emergency condition. Audible appliances must produce a sound level of at least 15 dB above the average ambient sound level, or 5 dB above the maximum sound level having a duration of at least 60 seconds, whichever is greater. In sleeping areas, the audible signal must be at least 75 dB at the pillow level. The standard fire alarm evacuation signal is the temporal-three pattern (three pulses, pause, repeat), which must be used for all new installations.
Visible Notification Requirements
Visible notification appliances (strobes) are required in public and common-use areas and where required by applicable building codes or the AHJ. The flash rate must be between 1 and 2 flashes per second. The intensity (candela rating) is determined by room size and geometry using spacing tables provided in the code. Wall-mounted appliances and ceiling-mounted appliances have different spacing tables. The minimum candela rating for wall-mounted strobes in a standard room is 15 cd, with higher ratings required for larger rooms.
Sleeping Area Considerations
Notification in sleeping areas has enhanced requirements. In addition to the 75 dB audible requirement, visible appliances rated at a minimum of 110 cd (wall-mounted) are required in sleeping rooms for hearing-impaired occupants. Low-frequency (520 Hz) audible notification appliances are required in sleeping areas to improve waking effectiveness, particularly for individuals with hearing loss.
Textual and Voice Notification
Where emergency voice/alarm communications systems are installed, Chapter 18 requires that voice messages be intelligible. The Intelligibility criteria ensure that spoken messages can be clearly understood by occupants. Voice systems must be designed to achieve a minimum speech transmission index (STI) or equivalent measure as specified in the code.
