... remote control operation (remote-control is optional units). Technical Specifications Detectable Gas 1Combustible / Flammable / Explosive gas ( H2, CH4, LPG, ... LELAlarm Threshold (two-stage) Low: 25% LEL / High: 50% LEL Detectable Gas 2Toxic / Poisonous gas ( H2S, CO, NH3, NO, NO2, ... parameter list (e.g. CO: 35 ppm / 70 ppm)Detectable Gas 3Oxygen (O2)Measuring Range0~30.0% VOLAlarm ThresholdLow: 18 ...