... . 1.We are one of the leading gas detecting tube and instruments supplier in China mainland. We have the ... granted the certificate of conformity by inspection department. Our detection tubes have also obtained Safety Certificate of Approval for Mining ... --CO, Carbon Dioxide--CO2, Oxygen--O2Wind direction(Smoking generating tube), Ammonia--NH3,Hydrogen Sulfide--H2S,Nitrogen Dioxide--NO2,Sulfur Dioxide ...