National Physical Laboratory

Accreditation and international comparability

UKAS ISO logos

ISO Guide 34 and ISO 17025 accreditation

NPL has an extensive scope of accreditation to ISO Guide 34 (Reference Materials) and ISO 17025 (Calibration) awarded by UKAS (the United Kingdom Accreditation Service).

International comparisons

NPL frequently participates in international comparison exercises with other National Measurement Institutes (NMIs). These comparisons, which are organised by the Consultative Committee for Amount of Substance (CCQM) of the International Committee for Weights and Measures (CIPM), provide a robust framework to demonstrate the global comparability of gas standard mixtures and measurements.

Calibration and Measurement Capabilities

Results of the comparisons operated by the CIPM CCQM are used to compile internationally-recognised Calibration and Measurement Capabilities (CMCs). A table of NPL's CMCs for gas analysis can be downloaded here.

Further information regarding international comparisons and CMCs can be found from the BIPM Key Comparison Database.


CIPM Mutual Recognition Arrangement

Certificates for gas mixtures covered by NPL's CMCs display the logo of the Mutual Recognition Arrangement (MRA) of the CIPM. Certificates containing this logo are mutually recognised by all NMIs who are signatories to the MRA.


Please email or telephone Customer Services on +44 20 8943 6151.

Last Updated: 16 Jun 2016
Created: 17 Sep 2013


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