Features: It is capable of detecting 4 kinds of gas: carbon monoxide(CO), hydrogen sulfide(H₂S), oxygen(O₂) and combustible gas(LEL). Premium material and selected top quality electronic components ensure excellent sensitivity and accurate measurement. Pocket-size, light weight and ergonomics design make it convenient to carry and use. Built in 2500mAh lithium-ion battery after a full charge allows this alarm to work for 8 hours operation, and work about 6 hours with external gas sampling pump. Backlight enables you to see the value clearly even in dark environment. 2 alarm methods: audio alarm and icons showed on the screen. Various functions meet your demand: gas monitoring, peak value display, low alarm setting mode, high alarm/TWA setting mode, etc. It is suitable to be used in petroleum, chemical industry, metallurgy, refining, etc.