This standard covers the determination of the concentration of H2S and CO2 in Natural Gas using a length of stain tube. The ranges covered is 3 ppmv to 5% by volume H2S and 0.25 to 10% by volume of CO2. The Method as written is applicable to the determination of H2S and CO2 in hydrocarbons and in air. The current revision updates some materials used in the procedures which by todays best practices would be found obsolete in terms of what we would use to collect or transport a sample to the stain tube, i.e. gum rubber tubing, etc. The most significant addition to the standard is the "Cautionary Statement." The intention of the statement is to inform the user that it is critical that manufacturer's instructions must be followed implicitly. Each lot of stain tubes is tested by the manufacturer for compliance to stated accuracy and each lot or box of stain tubes quite possibly is slightly different in terms of how they are to be used, i.e. exposure times, indicating colors or contaminants, etc. Further, the manufacturer's instructions will state the exponent to be used for multiple or partial testing "pulls" of the pump or if these are allowed at all. This information may very from lot to lot and from one brand of tube to another.