GASCO 34L-99-50, Hydrogen Sulfide (H2S) Calibration Gas also known as H2S Cal Gas, is used for the Calibration and Maintenance of Gas Detectors and Sensors. All of our GASCO Calibration Gas Cylinders ship with a COA (Certificate of Analysis). GASCO Calibration Gas meets or exceeds the requirements of the Original Gas Detection Equipment Manufactures Specifications.