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Author(s): Wayne Moore. Published on December 29, 2014.

RECENTLY, QUESTIONS HAVE ARISEN AT local contractor meetings about the fact that local authorities having jurisdiction have enforced something that the contractors did not believe appeared in the code. The jurisdiction had adopted the 2010 edition of NFPA 72®, National Fire Alarm and Signaling Code. The contractors questioned the requirements in section, which state that “effective January 1, 2014, where audible appliances are provided to produce signals for sleeping areas, they shall produce a low-frequency alarm signal that complies with the following: (1) The alarm signal shall be a square wave or provide equivalent awakening ability. (2) The wave shall have a fundamental frequency of 520 Hz ± 10 percent.”

Now that we’re a year past the implementation date for these requirements for sleeping areas, it’s worth a look back to see where they came from. The background for these requirements came from a Fire Protection Research Foundation study entitled “Waking Effectiveness of Alarm for Adults Who Are Hard of Hearing,” by Dorothy Bruck and Ian Thomas, researchers in the School of Social Science and Psychology at Victoria University in Melbourne, Australia. The Technical Committee added these requirements to the 2010 edition of the code in an attempt to accommodate those with mild to severe hearing loss. But Technical Committee members also understood that manufacturers needed time to design and produce an appliance that could meet these new requirements, which prompted the implementation date of January 1, 2014.

When any authority having jurisdiction, or AHJ, adopts the code, all the requirements in that code apply to new fire alarm system installations in that jurisdiction. This can result in confusion among users unfamiliar with the code process. Nevertheless, the intent remains clear: once the implementation date becomes effective, then all authorities having jurisdiction must begin to enforce the requirement.

Interestingly, when a building code or jurisdictional code required an in-building fire emergency voice/alarm communications system (EVACS) in a building, the low-frequency requirement became effective immediately upon the date of adoption for the 2010 edition of the code by that jurisdiction. The later effective date listed in Chapter 18 for using a low-frequency signal did not apply to Chapter 24 because installers can easily adapt voice systems to comply. The requirements of 18.4.5 apply to stand-alone, tone signaling appliances.

The code outlines the one exception to this requirement when it says that, “in areas where sleeping accommodations are provided, but the voice communication system is used to communicate to occupants who are awake, the low-frequency tone shall not be required.”

The reason for this exception, as stated in the annex for Chapter 24, arises “when sleeping accommodations are provided in occupancies such as healthcare, detention and correction, and other occupancies where it would not be necessary to utilize a low frequency tone that awakens those sleeping. For example, in a hospital, the voice message is used to notify staff members who are already awake. The staff will then respond to the appropriate location in the hospital to carry out their duties, which may include awakening and relocating patients who may be in danger. In addition, fire drills are required to be conducted on a regular basis, and providing a low-frequency tone could unnecessarily awaken patients, which would be detrimental to their care.”

This issue illustrates the importance for all stakeholders in a fire alarm system to learn how to navigate the code. How and when a particular requirement applies to a specific fire alarm system depends on many factors. Stakeholders must understand where, when, and how the requirements may apply to any particular fire alarm system.

WAYNE D. MOORE, P.E., FSFPE, is vice president at Hughes Associates.