The HFS-D Intelligent Non-Relay air duct smoke detector comes with the sensor head factory installed. HFS-D is used for detecting smoke and products of combustion present in air moving through an HVAC air handling system. When smoke is detected in a duct, the unit communicates the condition to the Fire-Lite MS-25 (E) Fire Alarm Control Panel. The panel, in turn, depending on programming and wiring, turns off fans, blowers, and other devices.
