ISO 33401:2024 (formerly ISO Guide 31) - Reference materials — Contents of certificates, labels and accompanying documentation
Documents accompanying reference materials (RMs) deliver users information that is essential for their proper use. For international harmonization of information conveyed by RM documents, ISO/TC 334, formerly the ISO Committee on Reference Materials (ISO/REMCO), published ISO Guide 31 since 1981. The most recent version of ISO Guide 31 was published in 2015, which especially focused on elaborating how documents for RMs in general and certified reference materials (CRMs) should be prepared. For example, statement of metrological traceability is essential for CRMs, but not for other types of RMs.
ISO 33401 is the new International Standard that was prepared by transforming ISO Guide 31:2015 into an International Standard. The Standard explains mandatory/recommended/optional contents of RM documents. It mostly follows ISO Guide 31:2015, but some technical changes and editorial changes were applied. For example, ISO 33401 requires property of interest to be stated for all types of RMs, because RMs function as RMs only for homogeneity- and stability-assessed properties. Further, considering the recent interest in digital certificates, it does not require page numbers to be stated on RM documents. Rather, it requires that all parts of the document be identified as part of the whole document. Other minor corrections were also applied.
The use of reference materials (RMs) is a key activity for the improvement and maintenance of a worldwide coherent measurement system. RMs with different characteristics are used in measurement processes, for the purpose of precision control, bias assessment, calibration, assigning values to other materials, and maintaining conventional scales, to name a few.
For the establishment of metrological traceability of measurement results to international scales or other measurement standards, proper use of certified reference materials (CRMs) is essential. From the perspective of a reference material producer, the documentation that is provided with an RM is the value-adding component of the material. For the user, the document is critical for the correct implementation and use of the RM in the measurement process.
Following ISO Guide 31, ISO 33401 is expected to be helpful for both RM producers and users in delivering and understanding information that is essential for the correct use of RMs.
Paper citations:
Saito, T. and Botha, A., "Guidance on the contents of accompanying documentation for reference materials (RMs)”, Accred Qual Assur (2016) 21: 239.
ISO Guide 31 - The ISO Committee on Reference Materials (ISO/REMCO) recognised the importance of the documentation that accompanies a reference material as early as 1981 when the first edition of ISO Guide 31 was published. The third edition of the Guide considered the appropriate accompanying documentation for all types of reference materials, i.e. CRMs and non-certified RMs.