[. . . ] Learn/Test Button Press the button to transmit a learn/test code, silence the alarm, test or recalibrate the Smoke Detector  Corner, top of an “A” frame type ceiling, near ceiling beams or over a cabinet – The stagnant air may affect sensor sensitivity. Operation Smoke Detection Upon smoke detection, the Smoke Detector LED will flash, and the buzzer will sound to raise alarm. [. . . ] Recalibrating the Smoke Detector Auto Calibration The operation condition of the Smoke Detector may vary sometime after installation, which may affect its smoke detection performance. In order to maintain its performance, the Smoke Detector will automatically recalibrate its sensor every month to ensure it is under optimal working condition. The Smoke Detector will not give any indication when it is performing auto calibration, unless the calibration process has failed. The Smoke Detector will enter calibration process when batteries are inserted. The Smoke Detector will still function normally when auto calibration fails by using previous calibration’s setting. Manual Calibration Follow below steps to manually recalibrate the Smoke Detector when auto calibration fails 1. Press and hold the learn/test button for 10 seconds until the LED begins to flash. Release the learn/test button, the Smoke Detector will emit 2 short beeps. When recalibration is complete, the Smoke Detector will emit 2 short beeps and the LED will turn off. If manual calibration still fails, the Smoke Detector will emit beeps, please remove the batteries, wait for 30 seconds then reload the batteries. Installation The Smoke Detector has 2 knockouts on the back cover for mounting on the ceiling. Use the two knockouts on the back cover to mark posittion on the ceiling. [. . . ] The Smoke Detector will enter self-calibrating process for 8-22 minutes after inserting batteries. Replace the Smoke Detector on the mounting bracket Specification Environmental Condition -10°C to 40°C, relative humidity 85% non-condensing. [. . . ]