On which side must duct detectors be installed?

Duct detectors must be installed on the supply side of the air handling system. This is critical because it allows the detector to sense smoke or other particulates entering the duct system before they can be distributed throughout the building. By monitoring the supply air, the system can effectively trigger alarms and activate fire protection measures if smoke is detected. This installation ensures early detection, which is essential for occupant safety and effective response during a potential fire emergency.

Positioning duct detectors in other locations, such as the return side or exhaust side, would not provide the same effective monitoring of air being delivered to occupied spaces, reducing their efficacy as a fire safety measure. Installing them outside would also be inappropriate as it would circumvent the purpose of detecting smoke within the ductwork itself.