The fire warning alarm tool is an active fire protection component of a fire alarm system. Notification tools may use audible, visible, or other stimuli to alert fire occupants or other emergency situations requiring action. Hearing instruments have been used longer than other notification methods. Most current equipment produces sound pressure levels between 45 and 120 decibels at ten feet.
Video Fire alarm notification appliance
Notification methods
The main function of the notification tool is to alert people at risk. Several methods are used and documented in the industry specifications issued by UL.
Warning methods include:
- Sound (audible signal)
- ~ 3Ã, kHz/~ 3100Ã, Hz tone (high frequency). Used on many current notification devices.
- 520Ã, Hz (low frequency). Used in newer notification devices.
- 45dB to 120Ã, dB A is weighted for human hearing (higher decibels, in the 100-120 dB range, common with older electromechanical horns)
- Light (visible signal)
- 15 cd to 1000 candela cd output
- 1 to 2 blinks per second
Maps Fire alarm notification appliance
Encoding
Coding refers to the pattern or tone of the notification tool that reads and controls either by the panel or by adjusting the jumper or DIP switch on the notification equipment. Most of the audible notification equipment that was installed before 1996 produced a stable sound for evacuation. In general, there is no general standard at the time that mandates a particular tone, or a pattern for evacuation alarms that can be heard. Although less common than stable sound, different signaling methods are used for the same purpose. These are named in connection with their typical structure and include, March Time (usually 120 pulses per minute but sometimes at 90 pulses or 20 pulses per minute depending on the panel), Hi-Lo (two different notes alternately), Slow- Shouts (slow strokes upward in tones) among others. Currently these methods are limited to applications intended to trigger a response other than evacuation only. In 1996, ANSI and NFPA recommended a standard evacuation pattern to eliminate confusion. The pattern is uniform regardless of the sound used. This pattern, also used for smoke alarms, is called the Three-Temporal alarm signal, commonly referred to as "T-3" (Temporal Pattern ISO 8201 and ANSI/ASA S3.41) and results in four interrupted interruptions (three pulses a second, followed by a one and a half second pause, repeated for a minimum of 180 seconds). The CO (carbon monoxide) detector is determined to use the same pattern using four pulse pulses (often referred to as T4).
Audibility
From NFPA 72, 2002 Edition: "7.4.2.1 * To ensure that public mode signals can be heard clearly heard, unless allowed by 7.4.2.2 to 7.4.2.5, they must have a sound level of at least 15 dB (Decibel) above the level the average ambient noise or 5 dB above the maximum sound level which has a duration of at least 60 seconds, whichever is greater, measured 1.5 m (5 ft) above the floor in a liveable area, using the A-weighted scale (dBA ). "
Visual signals
In 1970, Space Age Electronics introduced the first visual notification tool, the AV32 light plate (mounted on top of existing horns) and V33 long-distance lamps. Meanwhile, in 1976, Wheelock introduced the first horn/strobe notification equipment with the 700 x series. The majority of visual signals throughout the 1970s and 1980s were white or red incandescent. In the 1980s, most new installations began to incorporate visual signals, and more lights began to emerge. In the United States, 1990 Americans with Disabilities Act (ADA) triggered a shift in evacuation signaling methods to include hearing impairment. Notification devices that can be heard now should include a strobe light with a higher intensity of brightness to warn hearing loss. This makes incandescent lights inadequate for ADA purposes.
Many existing installations do not include visual signals installed with strobe plates. This retrofit plate will facilitate strobe installation without replacing audible signals. Then the ADA code also requires that the lamps be at least 15 glasses and have a flash rate of at least 60 flash per minute (one flash per second). Companies like Wheelock and Simplex stop translucent lights, and replace them with new, clear, and high-intensity lights. Today, sync strobe is often used to synchronize all the lights in a uniform flash pattern. This is to prevent individuals with photosensitive epilepsy because of potential seizures due to their non synchronized lights.
Voice evacuation
Voice evacuation system (also called Sound Alarm System) has become popular in most countries. Evacuation alarm sounds are usually not as loud as horns or bells (though generally the standard requires the same minimum sound pressure level), and it usually sounds an alarm tone (usually a slow tone, code-3, or a chime voice tone, though this depends on country and specific apps) and voicemail warnings that emergencies have been reported and to evacuate buildings (often also directing residents not to use elevators). Voice evacuation systems can also be used by personnel to provide specific direct information and/or instructions over an alarm system using a built-in microphone, which provides a distinct advantage over horns or bells. The system can be stand-alone (ie using a special loudspeaker, which can also feature integrated strobe lights), or the system can accommodate public address system functionality. In 1973, the fire alarm company Autocall produced the first sound evacuation system.
Voice evacuation in Europe
In Europe, a voice evacuation system is usually a mandatory requirement for rail and air transport terminals, high-rise buildings, schools, hospitals, and other large facilities. The sound system for emergency use dates back at least as far back as second world war. Following in the footsteps of companies like Avalon, Tannoy and Millbank Electronics etc., in the 1980s many other companies such as ASL, Application Solutions (Safety and Security) Ltd. started producing sound evacuation systems. In the 1990s, evacuation of sound began to become the standard for large facilities, and still continues to be popular. The use, design, operation and installation of the Voice evacuation system is set up in Europe by the European Committee of CENELEC for Electrotechnical Standardization EN 60849 and in the UK by British Standard BS 5839-Part 8, a code of system practice. This was followed by European equipment standards aligned Europe EN 54, and ISO 7240-16: 2007.
Effectiveness
Initial research on the effectiveness of various warning methods is very rare. From 2005 to 2007, research sponsored by NFPA focused on understanding the causes of higher mortality seen in high-risk groups such as the elderly, those with hearing loss, and those who were drunk. The research findings show that the output of low frequency square wave (520Ã, Hz) is significantly more effective in awakening high-risk individuals. Recent research has shown that strobe lights are not effective for waking sleeping adults with hearing loss and suggest that different alarm tones are much more effective. Individuals in hearing loss communities seek to change awareness raising methods.
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The NFPA study further demonstrates the increased effectiveness of the wake of low frequency quadratic auditory signals using 520 Hz, especially when used to wake people with mild to moderate hearing loss. Two separate studies were conducted - one for hard-of-hearing and one for alcohol-disorder - to compare the effectiveness of waking devices of low 520 Hz wave frequency and 3100 Hz pure T-3 sound devices.
Under test conditions, T-3 square wave waves of 520 Hz build 92% of participants with hearing loss, making it the most effective. A pure 3100 Hz T-3 sound alert woke 56% of the participants.
Summary of the research shows that the 520 Hz square-wave signal having at least 4 to 12 times more effective than the 3100 Hz signal at this time.
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Effective January 1, 2014, section 18.4.5.3 of the 2010 edition and newer editions of NFPA 72 require low-audible, low-frequency fire alarm signals in the sleeping area with protected building fire alarm systems. The Committee of Chapter 18 chooses to apply the requirements for all sleeping areas - not just places where residents identify themselves as people who have hearing impairments. This is done deliberately for several reasons: in many cases, the affected app is a lodging place like a hotel, and many people may not know that they have a hearing loss or they may have an alcohol disorder.
A low frequency signal of 520 Hz is required in the sleeping area of ​​the following buildings:
- Hotels and motels
- University and university dorms
- Retired/life-assisted facilities without trained staff responsible for waking patients
- Units live inside apartments and condominiums
According to NFPA 72-2010, section 18.4.5.3 *, audible equipment provided for sleeping areas to wake the occupants shall produce low-frequency alarm signals in accordance with the following (effective January 1, 2014):
- (1) The alarm signal must be square wave or give equivalent generating capability.
- (2) Waves must have a base frequency of 520Ã, Hz/- 10 percent.
See also
- Fire protection
- Active fire protection
- Passive fire protection
- Fire alarm control panel
- The fire alarm tower station
- Fire bills
- Fake alarm
- Fire alarm system
- Smoke detector
References
Further reading
- National Fire Protection Code, Article 72
- Underwriters Laboratories UL 217: Smoke Alarms Single Station and Multiple
- Underwriters Laboratories UL 1971: Signal Device for Hearing Loss
External links
- National Fire Protection Association
- NFPA study press release July 26, 2007: The effectiveness of audible alarms and unheard alternatives
- Photosensitivity and Seizure Resources at the Epilepsy Foundation
- Hearing Loss Association of America Trials: Current Smoke Alarms Can not Build Millions of Hearing Persons
- IMO/ISO 8201 Alarm Tone Table
- Visual Alarm Tech Bulletin
- http://www.systemsensor.com/en-us/Files/Sound-Files/520-hz-tone-low-frequency.mp3
Source of the article : Wikipedia
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