Comparison of ultra-trace water vapour in nitrogen (10 to 2000 nmol/mol)

Project Description

Measurements of water vapour at amount fractions below 2000 nmol/mol are critical for the control of the contamination of pure gases used in the micro-electronic and other process gas industries. Measurements in this range are extremely challenging because of the difficulty of handling ultra-pure matrix gases without introducing contamination, and often require extended flushing times to reach these levels. Since it is not possible to prepare or maintain artefact-based standards in this range, the dissemination of traceability depends on the availability of facilities capable of generating such low concentrations dynamically.

The project will compare facilities at four NMIs by means of two stable travelling standards. These will be commercial CRDS instruments and will be used in parallel. In order to validate the stability of the CRDS instruments they will be calibrated by the same laboratory (NIST) at the beginning and end of the circulation.

Aug 07 Start of circulation of travelling standard (NIST – NPL – PTB - NMIJ – NIST)
Jan 08 Completion of circulation
April 08 Compilation of results
June 08 Preparation of report

Final Report 2011-06-30

The project has been completed and the report can be downloaded here>>.