Chemical Metrology FAQsNPL provides world-class research, consultancy, calibrations and specialised measurement services in chemical metrology.
Below are answers to some frequently asked questions on NPL gas standards.
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- A flyer is available for download or you can contact us.
- In 1998, the Consultative Committee on Amount of Substance (CCQM) defined that traceability to the SI could only be achieved by the use of a primary method. In the case of gas standards the most relevant method is gravimetry.
- Certified Reference Materials (e.g. Primary Reference Gas Mixtures) produced by NPL under ISO Guide 34 will have an expiry date stated on the certificate.
- Calibrated Gas Mixtures (CGMs) are lower down in the gases hierarchy than PRGM or SGS.
- Primary Reference Gas Mixtures from NPL are prepared in a similar manner to the PSMs and are supplied to customers requiring the lowest uncertainties.
- NPL and other national standards laboratories around the world prepare primary standards of gas concentration, which they retain in-house as their ultimate reference for gas measurements. These primary standards are generally known as Primary Standard Gas Mixtures (PSMs).
- Secondary Gas Standards from NPL are certified directly against a selection of NPL PSMs using in-house validated analytical instrumentation which has demonstrated repeatability and linearity.
- This relates the different quality mixtures to each other.
- NPL offers a cost-effective re-certification service after the initial certification period has expired.
- Flyers are available for download or you can contact us.
Further Information
- NPL prepares an extensive range of traceable calibration gas standards with guaranteed relative uncertainties levels of 0.1% for certain species (PDF 676 KB).
- Accurate, nationally-traceable gas calibration standards (PDF 381 KB).