... chemical, the petroleum, the metallurgy, the fuel depot, the liquid gas station, the painting work ... , the fuel gas losing matches and so on flammable gas ... 220V±20%channel capacity /pipe capacity 100wire system 485bus-modetemperature -10°C~55°Crelative humidity ... level and diffferent digital unit detectors,Intelligent system:easy zero calibration,free relay output,4 ...