CCL - NOAA Global Monitoring Laboratory An official website of the United States government Here's how you know Official websites use .gov .gov website belongs to an official government organization in the United States. Secure .gov websites use HTTPS A lock ( ) or means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites. Global Monitoring Laboratory WMO GAW Central Calibration Laboratories NOAA GML is the World Meteorological Organization (WMO), Global Atmosphere Watch (GAW) Central Calibration Laboratory ( CCL ) for CO , CH , N O, SF , and CO. In support of GAW, GML offers calibration services for these gases for a fee. GML can also calibrate compressed gas standards to NOAA/GML internal scales for other gases, such as CFCs, HCFCs, and the stable isotopes of CO through our collaboration with the University of Colorado. About the GML CCL A WMO Central Calibration Laboratory is responsible for maintaining and distributing the WMO Mole Fraction scale for a specified gas in air. Products and Services GML sells and calibrates reference gas cylinders for a number of species. Calibration Scales Scales are defined based on a specific set of primary standards. Scales are named according to the year in which they are adopted. Calibration Results List results of calibrations performed by GML for CO , CO, CH , N O and SF on standard reference gas cylinders. The WMO CO scale has been revised. WMO CO X2025 has been applied to all calibrations since 1993. Additional Information Gravimetric Standards CO Manometer Scale Uncertainties Scale Transfer Uncertainties Updated April 2026 CO Scale conversion from X2007 to X2019 CO Analytical Method Preparation of Standards Regulator Guidelines Publications