... custom-made. 1.We are one of the leading gas detecting tube and instruments supplier in China mainland. We have ... in China. 2.Our company specializes in producing colorimetric gas detection tube. All kinds of tubes have been granted the ... . Carbon Monoxide, Carbon Dioxide, Oxygen, Wind direction(Smoking generating tube), Ammonia, Hydrogen Sulfide, Nitrogen Dioxide, Sulfur Dioxide, Chlorine, Benzene ...