Potter Fire Alarm Systems - Manual (Page 24)

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Fire Alarm Training • 8700055 • Rev F • 4/10
Notification
Audible and Visual Notification Appliances
The building code, AHJ or other governing code or standard determines the requirements for occupant notification. This
notification could be audible only, visual only or both. Once the notification requirement is determined by the appropriate source,
the required equipment shall be installed in accordance with the enforced version of NFPA 72.
Generally, notification is considered as horns, bells and strobes. However, notification also includes voice evacuation systems,
alarm printers, annunciators, textual displays and graphic displays. The standard dictates where and how these devices are
installed. Building codes call for the installation of voice evacuation systems. Insurance providers and certifying entities will
usually require the alarm printers. Authorities Having Jurisdiction will require the annunciators and graphic displays. Often,
the graphic displays are located near the front entrance to the building and provide a complete view of the building with alarm
points. Usually, remote annunciators will be located near the entrance where the emergency forces will enter the building. Some
authorities require that the annunciators utilize light emitting diodes (LEDs) and other will allow liquid crystal displays (LCDs).
Almost all installations require the use of audible signals through horns, bells or chimes. However, some cases exist that require
visual indicators. Visual indicators are accomplished through the use of flashing strobe lights. In some instances, a rotating beacon
is used for outdoor installations for warning on large industrial and commercial complexes. When the notification appliances are
required, calculations must be performed to ensure that the panel’s notification circuit will power all of the devices. In addition,
the standby batteries must be of sufficient size to power the panel in both a standby and alarm condition. Refer to the fire alarm
control panel installation instructions for further guidance on notification circuits.
Audible Notification
Audible notification has historically been used as a notification of fire. The early notification consisted primarily of bells or sirens.
An advantages of audible devices is that they have a low power draw therefore a circuit can have numerous devices connected to
it. In order for audible devices to alert the building occupants, the device must be loud enough to be heard. The level of loudness
is a measurement of sound pressure and that measurement is decibels or 1/10 bell. The decibels are expressed as dBA. This
measurement of decibels has been adjusted to account for the manner in which the human ear perceives different frequencies
in particular the way high-pitched (high frequency) sounds are heard better than low-pitched (low frequency) sounds. The A
weighting adjustment corrects for this so that the loudness at different frequencies can be heard. Most audible devices indicate the
sound pressure level at ten feet (XdB at 10 ft).
The sound level is required to be at least 15 dBA above the average or normal sound level or 5 dBA above the maximum sound
level that lasts at least one minute. This measurement is required to be 5 feet (1.5 M) off of the floor. The measurement in sleeping
areas is required to be measured at the pillow level. The Average Ambient Sounds levels are given below and only considered a
guide. Each installation is individual and will require specific evaluation.