... widely used in petroleum, chemical, environmental protection, metallurgy, refining, gas transmission and distribution, biological medicine, agriculture, etc 2. Technical ... . Detecting way:Ciffusion Type or Pump suction method Concentration unit:ppm,%VOL,%LEL,mg/m3 Acousto-optic alarm means:, ... show is as follows: the maximum range and the gas name Unit and electricity, 2 seconds later began to show ...