International comparisons of CO₂ in air standards (BIPM.QM-K2)

BIPM.QM-K2 is an on-demand key comparison for gaseous standards of CO₂ in dry air (part a) or in nitrogen (part b) contained in high pressure cylinders.

The Key Comparisons BIPM.QM-K2.a and b are aimed at underpinning the capabilities of the participants to value assign the amount fraction of CO₂ in air (part a) or in nitrogen (part b) in gas standards over the amount fraction range from 350 μmol mol⁻¹ to 800 μmol mol⁻¹, with a method ensuring traceability of the measurements to the SI.

The comparison is run as a series of bilateral comparisons between each participant and the BIPM. The facility maintained by the BIPM (the so called the CO₂-PVT facility) provides the Key Comparison Reference Value (KCRV) in each case and quantifies CO₂ amount fractions in air or nitrogen samples via measurements of the pressure and temperature of the sample and of the CO₂ extracted from it by cryogenic trapping. Its performance have been validated during the Pilot Study CCQM-P225 [1], and described in detail in a publication [2].

The comparison protocol and associated forms can be downloaded from this page. Completed registration forms should be sent to the comparison coordinator, Dr J. Viallon (BIPM).

[1] Viallon J., Choteau T., Moussay P., Wielgosz R., Veen A.v.d., Bi Z., Crotwell A., Hall B., Webber E.M. and Hill− Pearce R., 2023, Final report of CCQM-P225a and b, international comparison on carbon dioxide in air and nitrogen at ambient levels (350 μmol/mol to 800 μmol/mol), Metrologia, 60, 08029

[2] Viallon J., Meyer C.W., Moussay P., Schmidt J., Maxwell S.E., Arrhen F. and Wielgosz R., 2023, A high accuracy reference facility for ongoing comparisons of CO₂ in air standards, Metrologia, 60, 065014