Waking people during an emergency has always been a concern in the emergency notification sector, especially in the midst of a fire or carbon monoxide (CO) leak.
With that in mind, the National Fire Protection Association (NFPA) has emphasized the importance of abiding by two code updates that have changed what fire protection engineers, contractors and building owners need to know to protect building occupants.
The NFPA 72: National Fire Alarm and Signaling Code, effective Jan. 1, 2014, states that audible alarms in sleeping rooms must produce a low-frequency (520Hz) alarm tone to alert occupants of a fire in the building. This is known as a T3 tone pattern.
Additionally, the newly updated NFPA 720: Standard for the Installation of Carbon Monoxide (CO) Detection and Warning Equipment, effective Jan. 1, 2015, requires that a separate and distinct low-frequency tone is available to indicate the possible presence of CO. This is known as a T4 pattern.
However, what is most important to note about these two standards is that there are two completely different sound patterns based upon the detected condition in the occupied sleeping room.
Progression of NFPA 72 & 720 Updates
The original code updates date back to 2006 when new requirements were issued to optimize fire alarm notifications for high-risk groups such as those who are hard of hearing and alcohol-impaired adults. The codes were changed after studies with the Fire Protection Research Foundation found that a low frequency 520Hz square wave signal can awaken and alert at-risk individuals more effectively than a high-pitched tone.
Prior to this research, previous editions of the code did not specify a required frequency for audible tones. Most fire alarm and smoke alarm tones use sounders that produce high-frequency tones (3,150Hz) that fail to adequately wake high-risk groups since most adults experience hearing loss at this frequency.
The latest codes that went into effect this year can best be illustrated by the requirements outlined for the NFPA 720 code. The NFPA 720, 2012 edition, stated that an audible CO alarm signal (T4) shall comply with the following:
- Alarm signal shall be a square wave or provide equivalent waking ability.
- Wave shall have a fundamental frequency of 520Hz plus or minus 10 percent.
- The cycle of alarm tones can best be defined by the NFPA’s description that states signals shall be a single tone pattern consisting of four cycles of 100 milliseconds +/-10 percent “on,” and 100 milliseconds +/-10 percent “off,” followed by five seconds +/-10 percent”off.”
- After the initial four minutes of alarm, the five-second “off” time shall be permitted to be changed to 60 seconds +/-10 percent.
Chapter 6 of this code additionally includes important details on the physical construction of the devices used to comply with the code:
- Notification appliances used for CO signaling shall not have the word FIRE, or any fire symbol, in any form (stamped, imprinted, etc.) on the appliance visible to the public.
- Notification appliances with multiple visible elements shall be permitted to have fire markings only on those elements used for fire signaling.
The alarm signal shall be repeated in compliance with code chapters 5.8.6.5.1(1) and 5.8.6.5.1(2) until the alarm resets or the alarm signal is manually silenced. Similar regulations are in place for the NFPA 72 code with the main difference being the T3 pattern being administered from alerting.
NFPA’s Mandates for Sleeping Areas
The 2010 U.S. Fire Administration Study found that half of residential fire fatalities occur between 10 p.m. and 6 a.m., which emphasizes the importance of having fire alarm systems with effective waking alarms to give sleeping occupants the time needed to get to safety.
The updated codes apply to all areas intended for sleeping including: hotel/motel guest rooms; university dorm rooms; assisted-living facilities; and apartment living room areas where occupants might sleep. Hallways, lobbies and other tenantless places are not required to adhere to the NFPA 720 and 72 codes.
Author Ted Milburn is vice president of marketing for Eaton’s Life Safety & Mass Notification Solutions. This article originally appeared in CI sister publication Security Sales & Integration.
