Abstract: A duct mountable smoke detector includes a smoke sensor, an alarm indicating output relay, and an air flow control relay. In the presence of an alarm condition, the alarm indicating relay is energized thereby producing an alarm indicating signal. The air flow control relay is also energized thereupon changing an operative state of the respective air flow control element. Finally, a signal is coupled to an input/output interconnect port and, via an interconnect link, to other detectors coupled to the link. Other detectors coupled to the link which receive an alarm indicating interconnect signal energize the respective air flow control relays thereby changing operative state of the respective air flow control devices. The other detectors do not enter an alarm state. This allows for easy determination of the detector that initiated the alarm.