... 'an Hua Fan Instrument Co.,Ltd is one of the leading 12 portable gas alarming detector manufacturers and suppliers in China, welcome ... special separately)Destination gas: oxygen (O2), gas (EX), poisonous and harmful gases (CO, H2S, NH3, CL2, etc.)Response time: ≤30s(O2);≤ ... 40s(CO);≤20s(EX);Time display: the machine is year, month, day, and the clock display functionDisplay : ...