GASCO | Ammonia Calibration Gas | NH3 Calibration Gas | also known as Nh3 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. GASCO Calibration Gas is National Institute of Standards and Technology (NIST) Traceable, Made in the USA.