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LimWarLg.p65 01/10/2000
An automatic fire alarm system–typically made up of smoke
detectors, heat detectors, manual pull stations, audible warn-
ing devices, and a fire alarm control with remote notification
capability–can provide early warning of a developing 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 recommendations contained in the Guide for Proper Use
of System Smoke Detectors, which is made available at no
charge to all installing dealers. A study by the Federal Emer-
gency 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 de-
signed to provide early warning against fire, they do not guar-
antee 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 build-
ing. 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 be-
cause:
• 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 differ-
ent ways and are often unpredictable in their growth, neither
type of detector is necessarily best and a given type of detec-
tor 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 prede-
termined 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 lo-
cated, 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 responsibil-
ity 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. It is essential to use only equipment
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 Chapter 7 of NFPA
72 shall be followed. Environments with large amounts of
dust, dirt or high air velocity require more frequent mainte-
nance. A maintenance agreement should be arranged
through the local manufacturer's representative. Maintenance
should be scheduled monthly or as required by National and/
or local fire codes and should be performed by authorized pro-
fessional fire alarm installers only. Adequate written records
of all inspections should be kept.
While a fire alarm system may lower insurance
rates, it is not a substitute for fire insurance!
Fire Alarm System Limitations