The Gas Metrology Group periodically participates in bilateral and multi-laboratory international comparisons. During the past two years comparisons have taken place for sulfur dioxide, ethanol, propane, and hydrocarbon gas standards. Agreement of results allows for the claim of equivalence between national metrology institutes (NMIs) for the tested analytes and concentration ranges. This enables the use of gas standards obtained from the participating NMIs for regulatory purposes in the US.
The goal is to use the results from intercomparisons to assist in determining and correcting any large differences between gas standards from different NMIs. When results are within the stated uncertainty bounds, then the NMIs gas standards are considered to be equivalent. This enables the use of gas standards from the participating NMIs to satisfy regulatory compliance in other countries. An example is in the automobile industry where a manufacturer in Europe could use a gas standard from the Netherlands Measurement Institute (NMi) to comply with EPA regulations in the US. This is enabled by comparisons NIST has performed with NMi in the Netherlands. A yearly plan is agreed upon as to what analytes and concentrations will be compared between NIST and other NMIs. Standards from one NMI are analyzed by another or several other NMIs. Results of analyses are sent to the NMI whose standard is being compared. The analyzed value by a particular NMI is then compared to the value determined from the preparation data. NIST has routine comparisons with NMi in the Netherlands, NPL in the United Kingdom, and KRISS in Korea.