Fire alarm notification appliance

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A Wheelock MT-24-LSM electronic fire alarm horn and strobe.
A Wheelock MT-24-LSM electronic fire alarm horn and strobe.

A fire alarm notification appliance is an active fire protection component. A notification appliance may use audible, visible, or other stimuli to alert the occupants of a fire or other emergency condition requiring action.

Audible appliances have been in use longer than other methods. Today's appliances produce sound pressure levels between 45 and 120 decibels at ten feet.[citation needed]

The majority of audible notification appliances installed prior to 1996 produced a steady sound for evacuation. In general, no common standard at that time mandated any particular tone, or pattern for audible fire alarm evacuation signals. While less common than a steady sound, differing signalling methods were used for the same purpose. These are named with respect to their distinctive structure and include, March Time (120 pulses per minute), Hi-Lo (repeatedly changing tone), Slow-Whoop (slow rising sweep upwards in tone) among others. Today these methods are confined to applications intended to trigger a response other than evacuation alone.

In 1996, the ANSI and the NFPA recommended a standard evacuation pattern to eliminate confusion. The pattern is uniform without regard to the sound used. This pattern for smoke alarms is named the Code-3 temporal pattern (often referred to as T3) and produces an interrupted four count (three half second pulses, followed by a one and one half second pause). CO (carbon monoxide) detectors are specified to use a similar pattern using four pulses of tone (often referred to as T4).[citation needed]

In the United States, the 1990 Americans with Disabilities Act (ADA) triggered changes in evacuation signaling methods to include the hearing impaired. Audible fire alarm, would now include strobe lights to alert the hearing impaired.[citation needed] The 1996 ADA also required that the strobe lens be clear, at least 15 candelas, and with a flash rate of at least 60 flashes a minute.[citation needed] More recent research suggests that strobe lights are not effective at waking sleeping adults with hearing loss and suggest that a different alarm tone is much more effective.[citation needed] Individuals in the hearing loss community are seeking changes to improved awakening methods.[citation needed]

Older fire alarm notification appliances may have included incandescent lights as part of the audible appliance. Today, these are considered inadequate for the purposes of the ADA. These have been replaced by high intensity white strobe lights flashing at a uniform rate of between 1 and 2 flashes per second. In some cases this requires electronic synchronization of appliances supplied from different sources. Bells are often mounted onto plates that include a strobe unit on them. These are called retrofits. Although they are often used for bells, they are sometimes used for horns as well, often used to upgrade old fire alarm systems.

Contents

[edit] Alarms and alerts

The primary function of the notification appliance is to alert persons at risk. Several methods are used and documented in industry specifications published by UL.[citation needed]

Alerting methods include:

While current technology is very effective at detecting smoke and fire conditions, there have been concerns[who?] about the effectiveness of the alerting function in awakening sleeping individuals in certain high risk groups of people.[citation needed]

Initial research into the effectiveness of the various alerting methods is sparse. Recently (2005-2007), research sponsored by the NFPA has focused on understanding the cause of a higher number of deaths seen in high risk groups such as the elderly, those with hearing loss, and those who are intoxicated.[citation needed]

Research findings suggest that a low frequency (520 Hz) square wave output is significantly more effective in the high risk individuals at awakening. It is expected that products using the new alerting technology will be available in the future.[citation needed]

An older-style fire alarm vibratory horn with a double-projector and no strobe light.

A Simplex 4051 fire alarm electromechanical horn on a 4050-80 incadescent light plate.

A newer Simplex TrueAlert speaker/strobe.

A modern electronic horn/strobe made by Space Age Electronics.

An example of a fire alarm ADA retrofit, consisting of an old Simplex 4051 horn on a modern Faraday strobe plate.

An older Space Age Electronics 2DCD horn on a V33 light plate..

[edit] See also

[edit] Alarm manufacturers

[edit] References

  • National Fire Protection Code, Article 72
  • Underwriters Laboratories UL 217: Single and Multiple Station Smoke Alarms
  • Underwriters Laboratories UL 1971: Signaling Devices for the Hearing Impaired

[edit] External links


 v • d • e 
Fire protection
General: Active fire protection — Fire alarm system

Fire suppression: Fire extinguisher — Fire sand bucket — Fire sprinkler — Gaseous fire suppression
Detection/alarm: Control panel — Heat detector — Pull station — Fire alarm box — Notification appliance — Smoke detector
Practices: Fire drill — Fire drill regulations in the USA
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