Yondwin Gas Detector Alarm, Type of Gas Sensed: Natural Gas, Town Gas, LPG Mounted on the wall or cabinet, about 12 inches above the ground for LPG or 12 inches below the ceiling for coal gas and natural gas use. When the ignitable gas is detected, the red LED shall be flashed with alarm sound. If the sensor is invalid, the red indicator will be light and with sound continuous. After power-on, the relay output stop, the red indicator shall be flashed for preheating of sensor which is not in the normal operation of detection. After 3~4 minutes, the red indicator shall be stopped flash and green LED on for standby.