HCA Series Installation Manual
Page 6 of 58
V2.15
1.3 Fire Alarm System Limitations
An automatic fire alarm system
– in general is made up of smoke detectors, heat detectors, manual pull
stations, call points, audible warning devices, and fire alarm control panels with remote notification
capability, which can supply early warning of a developing fire. Such a system, on the other hand, is unable
to assure protection against property damage or loss of life resulting from a fire.
The manufacturer recommends that smoke and /or heat detectors must be positioned throughout a
protected premise following the recommendations of the current edition of the National Fire Protection
Association Standard 72 (NFPA 72), manufacturer’s 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 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. A fire alarm system may not provide timely
or sufficient notice, or might not function, for a diversity 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 or 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 the 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 photo electronic 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, both types of detectors are necessarily best and
a given type of detector may not provide adequate warning of a fire. A smoke detector 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 or combustion and alarm only when heat
on their sensors increases at a preset rate or reaches a predetermined level. Rate-of-rise heat detectors
may be subject to reduced sensitivity overtime. For this reason, the rate-of-rise feature of each detector
should be tested at least once per year by a qualified fire protection expert. 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 system for the connection of alarm transmission wiring, communications, signaling, and/or power. If
detectors are not located near the control panel, a developing fire may damage the alarm system, crippling
its ability to report a fire.
