The Model DS-SD Duct Smoke Detector detects the presence of smoke under extended temperature ranges in a building’s HVAC system. Its primary purpose is to provide early warning of the presence of smoke in the duct. It is typically used to detect smoke in the supply side of the HVAC system, but can provide supervision of the return side as well. The Model DS-SD detector is comprised of a plastic housing, a printed circuit board, a clear plastic cover, and an exhaust tube. The clear plastic cover permits visual inspections without having to disassemble the detector. The cover attaches to the detector housing using four captive screws and forms an airtight chamber around the sensing electronics. A sampling tube is required to introduce air into the duct smoke detector. The sampling tube is ordered separately and varies in length depending on the width of the HVAC duct. The DS-SD Addressable Duct Detector operates on all Kidde Fire Systems addressable fire alarm-suppression control units (Kidde, Fenwal and Chemetron brands) employing SmartOne communications protocol and can be mixed in any order with any current and legacy SmartOne detectors.