Audible notification requirements in sleeping areas were changed in the 2013 edition of NFPA 72. The 2010 edition first stated that as of January 1, 2014, audible notification appliances in sleeping area would be required to produce a 520 Hz tone.
Most fire alarm audible appliances produce a high frequency signal in the 3000 Hz range, which is in a range that many hearing impaired adults experience hearing loss. Research showed that a low frequency signal in the 520 Hz range could be used to awaken and alert hearing-impaired and alcohol-impaired individuals.
The intent of the requirement is that the 520 Hz tone be used in area intended for sleeping, but not throughout the entire building. For example, in an apartment or hotel unit, 520 HZ would be provided in the bedroom and living space of the unit but would not be required in common areas like hallways or lobbies.
The requirements of Chapter 18 (Notification Appliances) that cover 520 Hz audible notification in sleeping areas is only intended to address notification appliances connected to the building fire alarm or mass notification systems. For in room fire warning equipment (smoke alarms), the requirements of Chapter 29 (Single- and Multiple Station Alarm and Household Fire Alarm Systems) apply.
Application of Chapter 29 requirements are intended to be driven by other laws, codes, and standards. When another code requires single- and multiple stations alarms (smoke alarm), the requirements of Chapter 29 are intended to apply to apply. For example, both NFPA 101 and IBC require smoke alarms in apartment and hotel units. The requirements for the smoke alarms in these applications generally mirror the requirements of Chapter 29 in location of the devices.
Chapter 29 identifies two types of hearing loss with specific notification requirements. Mild to severe hearing loss low frequency audible notification, while moderately severe to profound hearing loss requires audible, visible notification and tactile notification (such as a bed shaker).
NFPA 72 simply states the requirements and does not specify exactly how the system shall be designed to meet these requirements. For example, the IBC requires that a specific number of rooms in I-1 (care facilities) and R-1 (hotels) have a strobe triggered by the building fire alarm and in-room smoke alarm.
One common method of meeting the requirements for 520 Hz audible and visible notification requirements is the use of an addressable fire alarm system. An addressable fire alarm system using smoke detectors with 520 Hz sounder bases can meet the audible notification requirements instead of smoke alarms. Rooms that require visible notification can have their strobe light driven by a notification module on the addressable system and be triggered by activation of either the in-room smoke detector or building fire alarm system. NFPA 72 permits the use of superior equipment, but designs using this configuration should still get written AHJ approval before moving forward.