... and toxic gases. It is suitable for combustible and toxic gas leakage detection in underground pipe or mines, and keeps the ... protection function;High concentration protection for combustible gas;Self test for the combustible gas sensor;Low battery indication;Replaceable sensor module ... and toxic gas, oxygen, Other rare toxic gas like NO,PH3,NH3,NO2,HCN,SO2 PH3,NH3,NO2,SO2 LCD CO Portable gas detector