Airflow in ventilation ducts is too fast for smoke detectors to detect. The solution is to install the detector inside a box containing a device to slow the flow of air across the detector.
The duct detector consists of a sealed box with a see-through cover that is installed on the returning air duct; a sampling tube for smoke input; and a smoke release tube - all of which are inserted into the duct via corresponding openings. The cover of the duct detector is translucent, allowing visibility of the internal chamber and the detector’s integral warning LED that is installed therein.
The DTH-400 / DTH-400A duct smoke detectors are intended to work with Telefire's conventional fire alarm control panels, models GSA-2B and GSA-1000 (DTH-400), and analog addressable fire alarm control panels model ADR-3000 (DTH-400A).
The duct detector allows sampling of airflow in return air vents of central ventilation systems.
The duct detector allows the use of photoelectric (TFO-440 / TFO-440A) smoke detectors.