2Johnson Controls, Inc. SLC Wiring Manual — P/N 51870:G 04/23/2009
Fire Alarm System Limitations
While a fire alarm system may lower insurance rates, it is not a substitute for fire insurance!
An automatic fire alarm system—typically made up of
smoke detectors, heat detectors, manual pull stations, audible
warning devices, and a fire alarm control panel with remote
notification capability—can provide early warning of a develop-
ing fire. Such a system, however, does not assure protection
against property damage or loss of life resulting from a fire.
The Manufacturer recommends that smoke and/or heat detec-
tors be located throughout a protected premise following the
recommendations of the current edition of the National Fire
Protection Association Standard 72 (NFPA 72), manufacturer's
recommendations, State and local codes, and the recommen-
dations contained in the Guides for Proper Use of System
Smoke Detectors, which are made available at no charge to all
installing dealers. These documents can be found at http://
www.systemsensor.com/html/applicat.html. A study by the
Federal Emergency Management Agency (an agency of the
United States government) indicated that smoke detectors
may not go off in as many as 35% of all fires. While fire alarm
systems are designed to provide early warning against fire,
they do not guarantee warning or protection against fire. A fire
alarm system may not provide timely or adequate warning, or
simply may not function, for a variety of reasons:
Smoke detectors may not sense fire where smoke cannot
reach the detectors such as in chimneys,in or behind walls, on
roofs, or on the other side of closed doors. Smoke detectors
also may not sense a fire on another level or floor of a building.
A second-floor detector, for example, may not sense a first-
floor or basement fire.
Particles of combustion or “smoke” from a developing fire
may not reach the sensing chambers of smoke detectors
because:
• Barriers such as closed or partially closed doors, walls, or
chimneys may inhibit particle or smoke flow.
• Smoke particles may become “cold,” stratify, and not reach
the ceiling or upper walls where detectors are located.
• Smoke particles may be blown away from detectors by air
outlets.
• Smoke particles may be drawn into air returns before
reaching the detector.
The amount of “smoke” present may be insufficient to alarm
smoke detectors. Smoke detectors are designed to alarm at
various levels of smoke density. If such density levels are not
created by a developing fire at the location of detectors, the
detectors will not go into alarm.
Smoke detectors, even when working properly, have sensing
limitations. Detectors that have photoelectronic sensing
chambers tend to detect smoldering fires better than flaming
fires, which have little visible smoke. Detectors that have ion-
izing-type sensing chambers tend to detect fast-flaming fires
better than smoldering fires. Because fires develop in different
ways and are often unpredictable in their growth, neither type
of detector is necessarily best and a given type of detector
may not provide adequate warning of a fire.
Smoke detectors cannot be expected to provide adequate
warning of fires caused by arson, children playing with
matches (especially in bedrooms), smoking in bed, and violent
explosions (caused by escaping gas, improper storage of
flammable materials, etc.).
Heat detectors do not sense particles of combustion and
alarm only when heat on their sensors increases at a predeter-
mined rate or reaches a predetermined level. Rate-of-rise
heat detectors may be subject to reduced sensitivity over time.
For this reason, the rate-of-rise feature of each detector
should be tested at least once per year by a qualified fire pro-
tection specialist. Heat detectors are designed to protect
property, not life.
IMPORTANT! Smoke detectors must be installed in the
same room as the control panel and in rooms used by the sys-
tem for the connection of alarm transmission wiring, communi-
cations, signaling, and/or power. If detectors are not so
located, a developing fire may damage the alarm system, crip-
pling its ability to report a fire.
Audible warning devices such as bells may not alert people
if these devices are located on the other side of closed or
partly open doors or are located on another floor of a building.
Any warning device may fail to alert people with a disability or
those who have recently consumed drugs, alcohol or medica-
tion. Please note that:
• Strobes can, under certain circumstances, cause seizures
in people with conditions such as epilepsy.
• Studies have shown that certain people, even when they
hear a fire alarm signal, do not respond or comprehend the
meaning of the signal. It is the property owner's responsi-
bility to conduct fire drills and other training exercise to
make people aware of fire alarm signals and instruct them
on the proper reaction to alarm signals.
• In rare instances, the sounding of a warning device can
cause temporary or permanent hearing loss.
A fire alarm system will not operate without any electrical
power. If AC power fails, the system will operate from standby
batteries only for a specified time and only if the batteries have
been properly maintained and replaced regularly.
Equipment used in the system may not be technically com-
patible with the control panel. It is essential to use only equip-
ment listed for service with your control panel.
Telephone lines needed to transmit alarm signals from a
premise to a central monitoring station may be out of service
or temporarily disabled. For added protection against tele-
phone line failure, backup radio transmission systems are rec-
ommended.
The most common cause of fire alarm malfunction is inade-
quate maintenance. To keep the entire fire alarm system in
excellent working order, ongoing maintenance is required per
the manufacturer's recommendations, and UL and NFPA stan-
dards. At a minimum, the requirements of NFPA 72 shall be
followed. Environments with large amounts of dust, dirt or
high air velocity require more frequent maintenance. A main-
tenance agreement should be arranged through the local man-
ufacturer's representative. Maintenance should be scheduled
monthly or as required by National and/or local fire codes and
should be performed by authorized professional fire alarm
installers only. Adequate written records of all inspections
should be kept.
Limit-C1-2-2007
