Final report on COOMET.QM-S2 (COOMET project no 556/RU/12): Comparison of primary standard gas mixtures: gravimetry production of CH 4 in synthetic air (100 µmol/mol)

Methane is one of the main components of greenhouse gases in the atmosphere. Its measurement is an important issue in monitoring changes in the global environment. The present comparison (methane in synthetic air at the level of 100 ?mol/mol) was proposed in 2011 within the cooperation program in the field of Metrology between VNIIM and INMETRO. It was then registered in the KCDB as a COOMET supplementary comparison with the identifier COOMET.QM-S2. The results of this exercise show that the primary standards of methane in air maintained by INMETRO and VNIIM are in good agreement, the difference of measurements being substantially smaller than its expanded uncertainty. The mixtures prepared for this exercise were found to be stable during about one year within the uncertainty of the measurements. Main text. 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 kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by COOMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).