FireNET FN-4127-NIC I & O Manual v1.0 UL
4
Test Weekly: The alarm system should be tested weekly to make sure all
sensors and transmitters are working properly. The most common cause of an
alarm system not functioning when a fire occurs is inadequate maintenance.
Alarms Cannot Guarantee Warning or Protection: Fire alarm system cannot
guarantee warning or protection against fire in every potential situation. 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.
Limitation on Fire Alarm Effectiveness: A fire alarm system may not provide timely or
adequate warning, or simply may not function, for a variety of reasons. For example:
No Detection: Particles of combustion or smoke from a developing fire may
not reach the sensing chambers of smoke detectors because:
1. Barriers (such as closed or partially closed doors, walls, or chimneys)
may inhibit particle or smoke flow.
2. Smoke particles may become cold, stratify, or not reach the ceiling or
upper walls where detectors are located.
3. Smoke particles may be blown away from detectors by air outlets.
4. Smoke particles may be drawn into air returns before reaching the
detector.
No Multi-Floor Detection: In general, smoke detectors on one level of a
structure cannot be expected to sense fires developing on another level.
Insufficient Smoke: 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 the detector, the detector will not go into alarm.
Smoldering vs. Flaming Fires: Smoke detectors, even when working properly,
have sensing limitations. Detectors that have photoelectric 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.
False Alarms and Pre-Fire Disconnection: Smoke detectors are subject to
false alarms and nuisance alarms and may have been disconnected by users.
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.
Fast Fires and Explosions: Smoke detectors cannot be expected to provide
adequate warning of fires caused by arson and children playing with matches
(especially within bedrooms), smoking in bed, violent explosions (caused by
escaping gas, improper storage of flammable materials, etc.).
Heat Detectors: Heat detectors do not sense particles of combustion and are
designed to alarm only when heat on their sensors increases at a
