A facility for the comparison of primary nitrogen monoxide gas standards is maintained at the BIPM. The NO facility enables the analysis of primary reference NO/N2 mixtures in the range (30 to 70) µmol/mol, with a measurement uncertainty of about 0.05 % approximately the same as the uncertainty of gravimetric preparation of such mixtures.
The original 15-port automatic sampler is complemented by an additional sampler unit capable of processing 30 cylinders simultaneously. The system is entirely automated by software developed at the BIPM. In 2005-2006 it was used as the central analytical facility for the international comparison of nitrogen monoxide gas standards (CCQM-P73) involving 12 NMIs and coordinated by the BIPM.
The facility is routinely used to label secondary gas standards used in the GPT facility, thereby providing traceability of the GPT system to the primary NO/N2 standards.
The facility is used on a periodic basis for international comparisons of nitrogen monoxide in nitrogen gas standards.