Simplex 4098 Applications Manual page 11

WHERE TO PLACE DETECTORS/SENSORS, Continued
Return
Correct
air
Figure 2. Detector Placement - Air Supply and/or Return Ducts
Smoke tests are helpful in determining proper placement. Special attention
should be given to smoke travel directions and velocity, since either can affect
detector/sensor performance.
Placement of a detector/sensor near air conditioning or incoming air vents can
also cause excessive accumulation of dust and dirt on the detector/sensor. This
dirt can cause the detector/sensor to malfunction and cause nuisance alarms.
Detectors/sensors should not be located closer than 3 feet (0.9 m) from an air
supply diffuser.
Spot type detectors/sensors, in properly engineered systems, may also be placed in
return air ducts, or in approved duct detector housings designed for this application.
Although duct detectors are not a substitute for open area detectors, they can provide
an effective method of initiating building control functions to prevent smoke from
being transported from the fire area to other parts of a building.
5
firealarmresources.com
Supply
Incorrect
air