Limitations of Fire Alarm Systems - Dated 5/13 Rev. B

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Limitations of Fire Alarm Systems

Manufacturer recommends that smoke and/or heat
detectors be located throughout a protected premise
following the recommenda
tions of the current edition of
the National Fire Protection Association Standard 72,
National F
ire Alarm Code (NFPA 72)
, manufacturer’s
recommendations, state and local codes, and the
recommendations contained in
Guide for the Proper Use of
System Smoke Detectors
, which is made available at no
charge to all installing dealers. A study by the Federal

Emergency Management Agency (an agency of the United
States government) indicated that smoke detectors may
go off or give early warning in as many as 35% of all
While fire alarm systems are designed to provide
warning against fire, they do not guarantee warning or
protection against fire. Any alarm system
is subject to
compromise or failure to warn for a variety of reasons.

Particles of combustion or "smoke” from a developing
fire may not reach the sensing chambers of the smoke
ctor because:


Barriers such as closed or partially closed doors,
walls, or chimneys may inhibit flow.


Smoke particles may become "cold” and stratify, and
may 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 reach
ing the detector.

In general, smoke detectors on one level of a structure
cannot be expected to sense fires developing on another

The amount of "smoke” prese
nt 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.

detectors, even when working properly, have
sensing limi
tations. Detectors that have photoelectronic
sensing chambers tend to detect smoldering fires better
than flaming fires, which have little visible smoke.
Detectors that have ionizing-type sens
ing chambers
tend to detect fast flaming fires better than smol
fires. Because fires develop in different ways and are
often unpredictable in their growth, neither type of
detector is neces
sarily best and a given type of detector
may not provide adequat
e warning of a fire.

Smoke detectors are subject to false alarms and
nuisance alarms. For example, a smoke detector located
in or near a kitchen may go into nuisance alarm during
normal operation of kitchen appli
ances. In addition,
dusty or steamy environ
ments may cause a smoke
detector to falsely alarm. If the location of a smoke
tor causes an abundance of false alarms or
nuisance alarms,
not disconnect the smoke detector;
call a professional to analyze
the situation and
recommend a solution.

ke detectors cannot be expected to provide adequate
ing of fires caused by arson, children playing with
matches (especially within bedrooms), smoking in bed,
violent explosions (caused by escaping gas, improper
storage of flammable materials, etc.).

Heat detectors do not sense particles of combustion and
are de
signed to alarm only when heat on their sensors
increase at a predetermined rate or reaches a
predetermined level.
Heat detec
tors are designed to
protect property, not life.

Warning devices (
including horns, sirens, and bells) may
not alert people or wake up sleepers who are located on
the other side of closed or partially open doors. A
warning device that activates on a different floor or level
of a dwelling or structure is less likely to awa
ken or
alert people. Even persons who are awake may not
notice the warning if the alarm is muffled by noise from
a stereo, radio, air conditioner or other appliance, or by
passing traffic. Audible warning devices may not alert
the hearing-impaired (strobes
or other devices should be
provided to warn these people). Any warning device may
fail to alert people with a disability, deep sleepers,
people who have recently used alcohol or drugs, or
people on medication or sleeping pills.


Please note that:


can, under certain circumstances, cause
seizures in people with conditions such as


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
responsibility to conduct
fire drills and other training exer
cises to make
people aware of fire alarm signals and in
struct on
the proper reaction to alarm signals.


In rare instances, the sounding of a warning
device can cause temporary or permanent hea

Telephone lines needed to transmit alarm signals from a
premises to a central station may be out of service or
temporarily out of ser
vice. For added protection against
telephone line failure, backup radio transmission
systems are recommended.

System components, though designed to last many
years, can fail at any time. As a precautionary measure,
it is recommended that smoke detectors be checked,
maintained, and replaced per manufacturer’s

System components will not work without electrical
power. If system batteries are not serviced or replaced
regularly, they may not provide battery backup when
AC power fails.

Environments with high air velocity or that are dusty or
dirty require more frequent maintenance.

In general, fire alarm
systems and devices will not work
without power and will not function properly unless they
are maintained
and tested regularly.

While installing a fire alarm system may make the owner
eligible for a lower insurance rate,
an alarm system is not
a substitute
Property owners should
continue to act prudently in protecting the premises and
the people in the premises and should properly insure life
and property and buy sufficient amounts of liability
insurance to meet their needs. Requirements and recommendations for proper use of fire alarm systems including
smoke detectors and other fire alarm devices:

Early fire detection is best achieved by the installation
and mainte
nance of fire detection equipment in all rooms
and areas of the house or bui
lding in accordance with the
requirements and recom
mendations of the current edition
of the National Fire Protection Association Standard 72,
National Fire Alarm Code (NFPA 72), the manufacturer’s
recommendations, State and local codes and the
ions contained in
Guide for the Proper Use of

System Smoke Detectors
, which is made available at no
charge to all installing dealers. For specific requirements,
check with the local Authority Having Jurisdiction (ex.
Fire Chief) for fire protec
tion systems.

Requirements and Recommendations include:

For residential applications, smoke detectors shall be
installed outside of each separate sleeping area in the
immediate vicinity of the bedrooms and on each
additional story of the family living unit, including

basements and excluding crawl spaces and unfin

Smoke detectors shall be installed in sleeping rooms in
new con
struction and it is recommended that they shall
also be installed in sleeping rooms in existing

It is recommended th
at more than one smoke detector
shall be installed in a hallway if it is more than 30 feet

It is recommended that there shall never be less

two smoke detectors per apartment or residence.

It is recommended that smoke detectors be located in
room where an alarm control is located, or in any
room where alarm
control connections to an AC source
or phone lines are made. If detectors are not so located,
a fire within the room could pre
vent the control from
reporting a fire.

All fire alarm systems
require notification devices,
including si
rens, bells, horns, and/or strobes. In
residential applications, each automatic alarm initiating
device when activated shall cause the operation of an
alarm notification device that shall be clearly audible in
all bedrooms over ambient or background noise levels
(at least 15dB above noise) with all intervening doors

It is recommended that a smoke detector with an
integral sounder (smoke alarm) be located in every
bedroom and an additional notification device be located
on each level of a residence.

To keep your fire alarm system in excellent working
order, on
going maintenance is required per the
manufacturer’s recommen
dations and UL and NFPA
standards. At a minimum the require
ments of Chapter 7
of NFPA 7
2 shall be followed. A maintenance agreement
should be arranged through the local manufacturer’s
representative. Maintenance should be performed
annually by authorized personnel only.

The most common cause of an alarm system not
functioning when a fire occurs is inadequate
maintenance. As such, the alarm system should be
tested weekly to make sure all sensors and transmitters
are working properly.

Wireless smoke detectors that are used in one-
and two
unit family dwellings may be used as long as the
rs are being monitored, tested, and maintained.
Once the detector is no longer part of a listed fire alarm
system monitoring program, it is recommended that it
be replaced prior to 10 years from the date of
manufacture per recommended practice of NFPA 72.

Any smoke detector, fire alarm system or any
component of that system which fails shall be repaired
or replaced immediately.

Typical System Installations per NFPA 72

As of March 2012, this document supersedes any previous liability information
with this product.


15144 5/13 Rev