Abstract
Main text Carbon monoxide (CO) in nitrogen was one of the first types of gas mixtures used in an international key comparison. This comparison dates back to 1998 (CCQM-K1a) [1]. Another key comparison on carbon monoxide is the CCQM-K51 at the lower amount fraction of 5 μmol/mol. Since then, many National Metrology Institutes (NMIs) have developed Calibration and Measurement Capabilities (CMCs) for these mixtures. Recently, NMIs in the APMP region have actively participated in international comparisons to provide domestic services. At the 2017 APMP meeting, several NMIs requested a CO comparison to establish CO/N 2 certification for supporting industrial needs, which was to be coordinated by KRISS. Consequently, this supplementary comparison provides an opportunity for APMP regional NMIs to meet their industrial needs. It is a replica of APMP.QM-S9.[2] To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).