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What is low frequency notification?
INTRODUCTION Today we will be discussing low frequency notification. Low frequency alarm signals were first introduced into the National Fire Alarm Code in the 2010 Edition of NFPA 72. All sleeping areas were required to be provided with low frequency alarm signals beginning January 1st of 2014. The alarm is required to produce a square wave or equivalent awakening ability with a fundamental frequency of 520 Hz. LOW-FREQENCY VS. HIGHER FREQUENCY (Play tone…..) The alarm notification you just heard is the 520 Hz low frequency Temporal Code 3 sounder. But why? What’s the reasoning for a low-frequency band as opposed to a standard frequency tone? WHAT IS LOW-FREQUENCY? Standard Temporal Code 3 notification appliances produce a high frequency sound of around 3150 Hz. Since the inception of Temporal Code 3 Alarm sound beginning on July 1st of 1996, many years of research has gone into what the most effective sound level is for providing an evacuation signal for all occupants of a building. The most important reason for low-frequency is waking up sleeping individuals during a fire. After about 20 years of research, low frequency sounders in a 520 Hz range were found to be most effective at waking sleeping occupants than the traditional 3150 Hz alarm. RESEARCH BASIS The low frequency alarm signal was found to be most effective for high-risk categories such as alcohol impaired individuals, young children, elderly, and those with hearing impairments. We needed, and found, a better method of waking especially high-risk sleeping occupants. In 2007, the fire protection research foundation published a report called Optimizing Fire Alarm Notification for high-risk groups. The purpose of the report was to try different alarms for notifying occupants of an emergency. The notification technologies tested included visual such as strobes and flashing lights, olfactory such as simulated smoke and pheromones and tactile including vibrating devices, moving air, and even electric shock. Haha. Out of all the technology tested, the low frequency sound wave was the most effective at awaking the high-risk category groups. INTRODUCTION OF THE REQUIREMENT So, when did it become a requirement? In the 2010 Edition of NFPA 72, Low frequency 520 Hz alarms were required for single and multiple station smoke alarms, smoke alarms not connected to a building fire alarm, where the occupants have mild to severe hearing loss per Section 29.3.8.1. The 2013 edition of NFPA 72 broadened the use of low frequency alarms by requiring all audible appliances initiated by the building fire alarm system that are provided in sleeping areas to wake sleeping occupants to be low frequency 520 Hz alarm. NFPA 72 Section 18.4.5.3 first appeared in the 2010 edition of NFPA 72 and stated the requirement is effective as of January 1st of 2014. NFPA 72 only mandates the use of low frequency 520 Hz alarm for a few specific cases (1) audible alarm, initiated by the building fire alarm system, in areas where the alarm is intended to wake sleeping occupants and (2) only for audible alarms initiated by smoke alarms, not initiated by the building fire alarm system, in sleeping areas where occupants have mild to severe hearing loss. There are additional guidelines outside of NFPA 72 as well. NFPA 101 REQUIREMENTS NFPA 101 Life Safety code requires where mandated by the occupancy chapter, all audible alarms in sleeping rooms initiated by the activation of a smoke alarm not the building fire alarm system must be a low frequency 520 Hz alarm, regardless of the hearing capabilities of the occupants. Two of the residential occupancy chapters in NFPA 101, new hotels and dormitories and new apartment buildings now require the use of low frequency alarms for audible notifications activated by both smoke alarms and the building fire alarm system. The key difference between NFPA 72 requirements and the NFPA 101 requirements, NFPA 101 now requires low frequency 520 Hz alarm regardless of the hearing capability of the occupants in that sleeping room, whereas NFPA 72 would only require low frequency alarms in those areas if the occupants have mild to severe hearing loss. What about the market? What has industry done? INDUSTRY CHANGES Although low frequency alarms have been around since the 2010 edition of NFPA 72, the market has not caught up to the requirement. Currently, there are no listed single station smoke alarms in the marketplace. Low frequency alarms require a high-fidelity speaker which in turn draw a significant amount of power. To produce the 75 Db at the pillow level required by NFPA 72, the size of the hardware required to produce the 520 Hz is much larger than the average single station or multiple station smoke detector footprint. With the higher draw, we may need fewer devices on a circuit or possibly larger batteries to back them up. Or even both. SUMMARY So, what is low-frequency in the fire alarm industry? Why use it? Why require it? Research has shown that low frequency 520 Hz notification appliances have proven to be most effective in alerting high risk categories such as children, the elderly, those with hearing impairments, and those under the influence of alcohol. The especially high-risk sleeping scenarios during a fire. Since the 2010 Edition, requirements for low-frequency audible notification has been incorporated in NFPA 72 as well as NFPA 101 to bring these features into fire alarm systems and help protect sleeping occupants from fire today. In our next video, we will discuss one-way emergency communication systems. Until next time, I’m Al Yakel, and this is MeyerFire University.
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