DW1401831 Rev.K1
Sep 18, 2015
13
8.3
Smoke detector applications
Smoke detectors are designed to sense the presence of smoke particles. In order to sense the particles, smoke
detectors must be placed where smoke can reach them. When determining the location of smoke detectors, potential
fire locations should first be evaluated, and paths of smoke flows should be determined. It is preferable to conduct
actual field tests wherever it is practical to do so. It is desirable to locate smoke detectors at the points of intersection of
smoke travel from potential fire sources throughout the area. Ceiling height, construction, and ventilation affect the
performance of smoke detectors.
8.3.1
Avoidance of unwanted alarms
Smoke detectors can be affected by various environmental factors (other than smoke), which may accidentally activate
the detectors. It is necessary to consider where smoke detectors should be installed in order to minimize unwanted
alarms. Listed below are some common sources of unwanted alarms to be considered when locating smoke detectors.
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Steam and moisture
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Chemical fumes
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Cooking equipment
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Welding, cutting, and industrial processes
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Dust or lint
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Engine exhaust
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Vibration or shock
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Excessive airflow
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Lightning
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Radio frequency radiation
The smoke detector signals a dirty sensor trouble to the control panel when it reaches the preset limit. The dirty sensor
trouble indicates the detector is in need of servicing.
8.3.2
Spacing of smoke detectors
The recommended spacing of spot type smoke detector is maximum 9.1 m (30 ft.), based on the detector installation
on a smooth ceiling at 3 m (10 ft.) high. All points on the ceiling shall have a detector within a distance equal to or less
than 0.7 times the nominal 9.1 m (30 ft.) spacing.
Note:
It is recommended that smoke detectors be installed on S = 9.1 m (30 ft.) centers, on smooth ceilings. Refer to
NFPA 72 National Fire Alarm Code for additional information on spacing adjustments.
Spot-type smoke detectors must be located on the ceiling or, if on a sidewall, between the ceiling and 30 cm (12 in.)
down from the ceiling to the top of the detector.
