1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA SBP 4-2015 Low-frequency Audible SignalsA NEMA Fire, Life Safety, Security, and Emergency Communication Section White Paper NEMA SBP 4-2015 Low-frequency Audible Signals Published by National Electrical Manufacturers Associa
2、tion 1300 North 17th Street, Suite 900 Rosslyn, Virginia 22209 www.nema.org 2015 National Electrical Manufacturers Association. All rights, including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic
3、Works, and the International and Pan American copyright conventions. NEMA SBP 4-2015 Page 2 2015 National Electrical Manufacturers Association Scope This white paper addresses the need for and development of the low-frequency audible signal used in fire alarms, carbon monoxide (CO) alarms, and fire
4、or CO alarm systems. It documents the signals waking effectiveness for hearing-impaired people, school-age children, and the elderly. It also summarizes the voluntary national consensus requirements for the application, installation, location, and performance for these products when employing the lo
5、w-frequency audible signal. Purpose The purpose of this white paper is to clear up confusion in the fire alarm industry related to application of the low-frequency audible alarm signal. It is ideally suited for installers, the fire service, building code officials, end users, fire protection enginee
6、rs, and electrical engineers. Introduction The majority of traditional fire or CO alarm notification appliances produce an audible signal with a frequency range between 2 kHz and 4 kHz. The traditional integral sounders used in almost all smoke or CO alarms also produce a 3 kHz audible alarm signal.
7、 By contrast, the low-frequency audible alarm signal has a fundamental frequency of 520 Hz. Researchers have been testing the effectiveness of various alarm signals and frequencies in waking various at-risk population subgroups. Much of this research has been conducted by Dr. Dorothy Bruck and her c
8、olleague Ian Thomas at Australias Victoria University. Their findings conclude that most unimpaired adults will normally awaken quickly to a 3 kHz audible alarm signal, and the low-frequency signal is most effective at waking high-risk segments of the population, such as people with hearing loss, th
9、e elderly, school-age children, and the alcohol impaired. Important Statistics Alarms and alarm systems provide life-saving value when occupants are awake, but their greatest benefit might be when the occupants are asleep. This is illustrated in a 2010 U.S. Fire Administration (USFA) study1, which r
10、eports that 50% of fire fatalities in residential buildings occur between the hours of 10:00 p.m. and 6:00 a.m., when most people are sleeping. According to a 2008 study2, most unimpaired adults wake up quickly to the “standard” 2-4 kHz audible fire alarm signal, even at levels well below 75 dBA. Bu
11、t 13%of fire fatalities in residential buildings involve children younger than 10 years old, and 44% of fire fatalities are adults between the ages of 40 and 69. Also, according to another study3, there are more than 34.5 million hearing-impaired people in the US. Research on Waking Effectiveness of
12、 Audible Alarm Signals For more than a decade, researchers have been testing the effectiveness of audible fire alarm signals at waking various at-risk population groups. The National Fire Protection Association (NFPA) Fire Protection Research Foundation has been instrumental in funding many of these
13、 studies. The 2008 report concludes that most unimpaired adults will wake quickly to the sounding of their smoke alarm, even at levels well below 75 dBA, the level at the pillow required by code. However, a number of groups might not wake as quickly, including people over 65, the hearing impaired, t
14、he alcohol impaired, and children. 1 Federal Emergency Management Agency, U.S. Fire Administration, Civilian Fire Fatalities in Residential Buildings (2008-2010), Topical Fire Report Series, Vol. 13, No. 1, Emmitsburg, Maryland. 2 Ian R. Thomas and Dorothy Bruck, Awakening of Sleeping People: a Deca
15、de of Research (Melbourne, Australia: Centre for Environmental Safety and Risk Engineering), 2008. 3 Ian R. Thomas and Dorothy Bruck, Waking Effectiveness of Alarms for Adults Who Are Hard of Hearing (Melbourne, Australia: Victoria University), National Fire Protection Association, 2007. NEMA SBP 4-
16、2015 Page 3 2015 National Electrical Manufacturers Association A series of tests was conducted with different groups of subjects. Variables included sound intensity (in dB) and frequency (in Hz) of the alarm signal, as well as other stimuli, including voice, strobe lights, and bed and pillow shakers
17、. Each test was constructed differently, so the findings between them are not directly comparable, but they were consistent over multiple studies. They showed the waking effectiveness of the 520 Hz signal with appropriate harmonics, as explained in Underwriters Laboratories LLC (UL) Product Standard
18、s section, was superior to that of the ”standard” alarm signal, as follows: a) Six to ten times more effective at waking children. b) Six to ten times more effective at waking young adults, both sober and with .05 blood alcohol level. c) Six times more effective at waking adults with hearing loss. W
19、hile a mothers voice might be effective at waking a child, voice was not a universally successful stimulus and presented particular problems for nonEnglish-speaking participants. More recent research, also by Dr. Bruck, with colleagues Chris Lykiardopoulos and Michelle Ball, confirms similar results
20、 with “hypnotics” (i.e., sleep-inducing drugs). This work had not yet been published at the time this white paper was published. Low Frequency Requirements in NFPA 72, The National Fire Alarm and Signaling Code, 2013 Edition Chapter 18 covers notification appliances that are connected to a protected
21、 premises fire alarm system. Effective January 1, 2014, section 18.4.5.3 requires that audible notification appliances installed in all sleeping areas produce a low-frequency audible alarm signal. Chapter 29 covers single- and multiple-station smoke alarms and household fire alarm systems. Unlike 18
22、.4.5.3, section 29.3.8 requires a low-frequency audible alarm signal in sleeping rooms and guest rooms only for those with mild to severe hearing loss or where required by a local law or code. The effect of 29.3.8 is that when smoke alarms and household fire alarm systems are installed in sleeping r
23、ooms, the low-frequency audible alarm signal is required only when the person with the mild to severe hearing loss chooses it. Low Frequency Requirements in NFPA 720, Standard for the Installation of Carbon Monoxide (CO) Detection and Warning Equipment, 2015 Edition NFPA 720 chapter 6 covers notific
24、ation appliances connected to a protected premises CO detection system. Effective January 1, 2015, audible appliances provided for the sleeping areas will be required to produce a low-frequency audible alarm. The scope of chapter 9 covers “Single- and Multiple-Station Alarms and Household Carbon Mon
25、oxide Detections Systems.” Section 9.4.2.2.1 requires a low-frequency alarm signal in sleeping rooms and guest rooms only for those with mild to severe hearing loss. The effect of 9.4.2.2.1 is that when CO alarms and household CO systems are installed in sleeping rooms, the low-frequency audible ala
26、rm signal is required only when the person with the mild to severe hearing loss chooses it. Low Frequency Requirements in Underwriters Laboratories LLC (UL) Product Standards In April 2012, UL published revisions to ANSI/UL 464, Standard for Audible Signal Appliances, and ANSI/UL 217, Standard for S
27、ingle and Multiple Station Smoke Alarms, both of which contain new performance requirements for the low-frequency signal. The signal is tested using audible spectral analysis, which confirms that the odd harmonics (F1, F3, F5, and F7) adhere to specific minimum sound level requirements. F1 (520 Hz)
28、is required to produce the maximum sound pressure level (dB). Each successive odd harmonic is required to produce the following: a) at least 5 dB less than F1; b) no less than 20 dB below F1 for the third harmonic; NEMA SBP 4-2015 Page 4 2015 National Electrical Manufacturers Association c) no less
29、than 30 dB below F1 for the fifth harmonic; d) no less than 50 dB below F1 for the seventh harmonic (see figure below). Audible notification appliances listed as complying with UL 464 must be marked with the words “low frequency alarm” on the exterior housing. Smoke alarms that meet these requiremen
30、ts must be permanently marked with the words “low frequency alarm.” These new requirements allow manufacturers to design, manufacture, and list products for low frequency applications, while allowing installers and code enforcement officials to easily identify low-frequency sounders by looking for t
31、hese words on the audible notification appliance or smoke alarm. For Emergency Voice Evacuation Systems, speakers are not required to be marked, but a letter of performance compliance is required from UL stating that the system amplifier, tone generator, and specific speaker properly generate the re
32、quired 520 Hz signal. While UL 2034, Standard for Single and Multiple Station Carbon Monoxide Alarms, does not currently include the low frequency testing provision, CO alarms can be tested and listed to the low frequency requirements in UL 217. Installation Requirements For installations that are d
33、esigned to comply with section 18.4.5.3 of NFPA 72, National Fire Alarm and Signaling Code, 2013 Edition, or with section 6.4.4.3 of NFPA 720, Standard for the Installation of Carbon Monoxide (CO) Warning Equipment, 2015 Edition, the low-frequency audible signal is required for notification applianc
34、es installed in all sleeping units of hotels, motels, dormitories, and within dwelling units of apartment buildings where there is a protected premises fire alarm system that activates the building-wide occupant notification system. The low-frequency audible alarm signal is required to be synchroniz
35、ed with other nonlow-frequency audible fire alarm signals within each notification zone. However, the low-frequency audible signal can be used throughout the protected premises. The low-frequency audible signal is not required to be installed in hospital patient rooms, jail cells, or other occupanci
36、es where the audible signal is not intended to wake sleeping people, because these occupancies have trained staff who are responsible for waking people in the event of a fire or a CO leak. For installations that are designed to comply with section 29.3.8 of NFPA 72, National Fire Alarm and Signaling
37、 Code, 2013 Edition, or with section 9.4.2.2 of NFPA 720, Standard for the Installation of Carbon Monoxide (CO) Warning Equipment, 2015 Edition, the low-frequency audible signal applies to alarms, alarm accessories, and household systems. The low-frequency signal can be provided voluntarily for thos
38、e with hearing loss or where required by local codes. The result is that occupants who provide their own equipment can choose whether or not a low-frequency alarm signal is right for them. NEMA SBP 4-2015 Page 5 2015 National Electrical Manufacturers Association Field verification testing of the low
39、-frequency audible alarm signal is not required, but visual confirmation of the marking and compliance is necessary. Power Considerations Notification appliances that produce the low-frequency audible signal draw more current than the traditional 2-4 kHz audible signal. Due to the comparatively high
40、 current draw of the low-frequency sounder, accurate voltage drop calculations and power supply selection are critical to ensure adequate current to the notification appliance circuit. The higher current draw of the low-frequency signal has caused considerable challenges for smoke alarm and CO alarm
41、 manufacturers. Consequently, at this time there are no smoke alarms or CO alarms with an integral sounder that produces the low-frequency audible signal. However, there are listed alarm accessory devices that provide the low-frequency audible fire alarm signal. NFPA Standards Impact on Model Codes
42、Section 907.2 in the 2012 edition of the International Fire Code (IFC) and International Building Code (IBC) requires a fire alarm system to be installed in new buildings in accordance with NFPA 72 to provide occupant notification in accordance with section 907.5 of the IFC/IBC. The basic purpose of
43、 a fire alarm system is to alert all occupants in a building. Section 907.5 requires activation of a fire alarm system to send a signal to the control unit and then provide occupant notification throughout all occupied areas of a building, including both common and tenant spaces. Common spaces are t
44、he corridors, lobbies, or meeting rooms. Tenant spaces are dwelling units within apartment buildings, guest rooms of hotels, or dormitory sleeping rooms. NFPA 72 and section 907.2 of the IFC/IBC do not apply retroactively to existing systems. However, there are situations when the Authority Having J
45、urisdiction might require an existing system to be brought up to current code requirements even though the system still meets the minimum code requirements of the version in effect at the time of the original installation. The 2010 edition of NFPA 72 is referenced in chapter 80 of the IFC and chapte
46、r 35 of the IBC. NFPA 72 section 18.4.5.3 requires the low-frequency signal to wake sleeping people in all occupancies having a protected premises fire alarm system. Section R314 in the 2012 edition of the International Residential Code (IRC) does not require low frequency notification in one- and t
47、wo-family dwellings beyond the requirements of NFPA 72 or NFPA 720, which stipulate the notification be provided when occupants self-identify. Product Solutions NEMA member companies provide numerous product solutions for designers and installers who need to comply with the low-frequency audible ala
48、rm requirements. Below are product solutions for installations that are designed to comply with section 18.4.5.3 of NFPA 72, 2013 Edition, or with section 6.4.4.3 of NFPA 720, 2015 Edition: a) Horns and horn/strobes that provide the low-frequency audible fire alarm signal; b) Smoke and CO detectors
49、with integral sounder bases that provide the low-frequency audible fire alarm signal; c) Emergency Voice Alarm Communication (EVAC) systems that provide a low-frequency pre-alert audible fire alarm signal. Below are product solutions for installations that are designed to comply with section 29.3.8 of NFPA 72, 2013 Edition, or with section 9.4.2.2 of NFPA 720, 2015 Edition: NEMA SBP 4-2015 Page 6 2015 National Electrical Manufacturers Association a) Household fire alarm and CO systems that provide the low-frequency audible fire alarm signal. b) At this time there are no smoke
