Limitations of Fire Alarm Systems



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Document Transcript

Limitations of Fire Alarm Systems

Manufacturer recommends that smoke and/or heat
detectors be located throughout a protected premise
following the recommendations of the current edition of
the National Fire Protection Association Standard 72,
National Fire 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
not
go off or give early warning in as many as 35% of all
fires.
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.
For
example:

Ȋ

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

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

Smoke particles may become "cold” and stratify, and
may not reach the ceiling or upper walls where
detectors are located.
Ȭ

Smoke particles may be blown away from detectors
by air outlets.
Ȭ

Smoke particles may be drawn into air returns
before reaching the detector.
In general, smoke detectors on one level of a structure
cannot be expected to sense fires developing on another
level.
Ȋ

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.
Ȋ

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 ionizing-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.
Ȋ

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 appliances. In addition,
dusty or steamy environments may cause a smoke
detector to falsely alarm. If the location of a smoke
detector causes an abundance of false alarms or
nuisance alarms, do
not disconnect the smoke detector;
call a professional to analyze
the situation and
recommend a solution.

Ȋ

Smoke detectors cannot be expected to provide adequate
warning 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.).
Ȋ

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

Ȋ

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 awaken 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.
Ȭ

Please note that:
’Ǽ

Strobes can, under certain circumstances, cause
seizures in people with conditions such as
epilepsy.
’’Ǽ

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 exercises to make
people aware of fire alarm signals and instruct on
the proper reaction to alarm signals.
’’’Ǽ

In rare instances, the sounding of a warning
device can cause temporary or permanent hearing
loss.
Ȋ

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

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
recommendations.
Ȋ

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.
Ȋ

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 for
insurance.
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 maintenance of fire detection equipment in all rooms
and areas of the house or building in accordance with the
requirements and recommendations 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
recommendations 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 protection systems.
Requirements and Recommendations include:
Ȋ

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 unfinished
attics.
Ȋ

Smoke detectors shall be installed in sleeping rooms in
new construction and it is recommended that they shall
also be installed in sleeping rooms in existing
construction.
Ȋ

It is recommended that more than one smoke detector
shall be installed in a hallway if it is more than 30 feet
long.
Ȋ

It is recommended that there shall never be less than
two smoke detectors per apartment or residence.
Ȋ

It is recommended that smoke detectors be located in
any 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 prevent the control from
reporting a fire.
Ȋ

All fire alarm systems require notification devices,
including sirens, 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
closed.
Ȋ

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.
Ȋ

To keep your fire alarm system in excellent working
order, ongoing maintenance is required per the
manufacturer’s recommendations and UL and NFPA
standards. At a minimum the requirements of Chapter 7
of NFPA 72 shall be followed. A maintenance agreement
should be arranged through the local manufacturer’s
representative. Maintenance should be performed
annually by authorized personnel only.
Ȋ

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.
Ȋ

Wireless smoke detectors that are used in one- and two-
unit family dwellings may be used as long as the
detectors 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.
Ȋ

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

DINING
KITCHEN
BEDROOM
BEDROOM
BEDROOM
LIVING ROOM
BEDROOM
TV ROOM
KITCHEN DINING
BDRM
BDRM
LIVING ROOM
LIVING
ROOM
BEDROOM
BEDROOM
BEDROOM
KITCHEN
TO
BR
CLOSED
DOOR
BASEMENT
GARAGE
- Smoke Detectors required
- Smoke Detectors required with integral
sounders recommended
- Heat Activated Detectors required
- Smoke Detectors for additional protection
- Notification Devices
floor_plan-003-V0

Typical System Installations per NFPA 72


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

Ê800-15144#Š
800-15144 5/13 Rev A


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