The Trane SEN01789 Photoelectric Smoke Detector Sensor is a safety component designed for compatible HVAC and building air management systems. It uses photoelectric technology to detect smoke particles by monitoring changes in light within its sensing chamber, triggering an alarm or control response when smoke is detected. Commonly used in compatible air handling units and ventilation... https://www.partshnc.com/trane-sen01789-photoelectric-smoke-detector-sensor