Audible for All
How can we ensure the alarm reaches the hearing impaired?
NFPA Journal®, January/February 2010
The 2010 edition of NFPA 72®, National Fire Alarm and Signaling Code®, has new requirements to help ensure that the audible alarm signal will reach even individuals with a mild to severe hearing impairment. For public-mode signaling, the code has always required that the audible notification appliances in a protected area deliver a sound level of at least 15 dB above the average ambient sound level or 5 dB above the maximum sound level for at least 60 seconds. For sleeping areas, the code requires that audible notification appliances either deliver these sound levels or a minimum of 75 dBA, whichever is greater.
Unfortunately, these requirements only benefit individuals who do not suffer from hearing loss or impairment. Until recently, the code accommodated people with mild to severe hearing loss who would not be awakened by the audible alarm by requiring the use of visible notification appliances.
Based on recent research, the Technical Committee on Notification Appliances has added a new requirement to the 2010 edition of the code. Effective January 1, 2014, non-voice audible appliances for sleeping areas must 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."
The 2014 date gives appliance manufacturers the time they need to develop products that will comply with this new requirement.
The effective date does not apply to fire alarm systems that use speakers to deliver audible notification signals. In such systems, a relatively simple programming change will produce the required low-frequency tone. For occupancies that provide sleeping accommodations, Chapter 24 of the 2010 edition of NFPA 72 requires the pre-alert tone to include a low-frequency component, consisting of a 520 Hz square wave ± 10 percent, to alert the hearing impaired to emergency voice messages. The low-frequency tone will help awaken such occupants to ensure that they will hear subsequent information.
After the NFPA membership adopted this edition of the code, technical committee members realized that the current wording would not be appropriate in certain sleeping accommodation occupancies where the voice communications system is only intended to notify staff to take appropriate action. Examples of such occupancies include health care facilities, day care facilities, and detention facilities. Unless NFPA modifies this code section, the requirement to provide the 520 Hz tone would conflict with, or prove detrimental to, building emergency evacuation plans in these occupancies.
To correct this unintended consequence, a tentative interim amendment, TIA Log 971, that addresses facilities where the 520 Hz should not be used is currently being circulated for comment. Essentially, the proposed TIA would not require the use of the low-frequency tone for those areas with sleeping accommodations where the emergency voice communication system communicates only to occupants who are awake.
The TIA proposes Annex A material stating that "the staff will then respond to the appropriate location…to carry out their duties...."
Users of the 2010 edition of NFPA 72 should note this new requirement for occupancies that provide these types of sleeping accommodations. They should also remain alert to changes to the code made by this and other TIAs to ensure full compliance with the code.
Wayne D. Moore, P.E., FSFPE, is a principal with Hughes Associates and immediate past chair of the NFPA 72 Technical Correlating Committee.