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SECTION V
DETECTOR APPLICATION AND SPACING
1. SMOKE DETECTORS
1.1 DESCRIPTION AND FUNCTION
Smoke detector is the generic name given
to either ionization type or photoelectric type
detectors. The ionization type responds to
both visible and invisible products of com-
bustion, while the photoelectric type de-
pends on sensing visible smoke.
1.2 SPACING
For average areas with smooth ceilings and
normal air movement, the maximum recom-
mended spacing is 900 square feet or no
more than 30 feet between centers and 15
feet from a sidewall. In areas with higher air
movement, the detector spacing should be
reduced accordingly.
1.3 APPLICATION LIMITATIONS
1.3.1 On ceiling heights below 8 feet, the
possibility of unintentional alarms from
tobacco smoke does exist, especially in
areas where people might congregate. It is
recommended that smoke detectors in such
areas have their zones wired through the
RC-30U alarm confirmation module.
1.3.2 Smoke detectors should not be used
in areas where they could be subjected to
steam or moisture condensation such as in
galleys, laundries, etc. Thermal detectors
should be used in such areas.
2. THERMAL DETECTORS
2.1 DESCRIPTION AND FUNCTION
All thermal detectors respond only to exces-
sive heat, which is assumed to be generated
from a flaming fire. The detectors are de-
signed with different operating principles as
described below.
2.1.1 Fixed Temperature
The air temperature has to exceed the set
ratings of the devices in order to activate it.
The settings are 135° F, 190° F, and higher
(on special order).
2.1.2 Rate Compensated
This type of thermal detector is similar to the
fixed temperature detector in operation, but is
compensated to eliminate the expected
thermal lag and, therefore, responds faster.
2.2 SPACING
Maximum approved spacing of thermal detectors
is as follows:
Maximum
Area Protected Distance from
Type (Square Feet) Sidewalls (Feet)
Fixed Temperature (DT-11) 625 (25 X 25) 12.5
Fixed and
Rate of Rise 2500 (50 X 50) 25
DT-135 CS, CL, and WP
Rate Compensated 2500 (50 X 50) 25
DT-200 CS, CL and WP
Rate Compensated 2500 (50 X 50) 12.5
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