A Procedure for Establishing Traceability of Gas Mixtures to Certain National Bureau of Standards Standard Reference Materials

摘要

This procedure includes the specifications and requirements that must be followed by gas manufacturers during the preparation of compressed cylinder gas Certified Reference Materials (CRM). A CRM is a certified gas standard prepared at a concentration that does not exceed + or - 1 percent of currently available National Bureau of Standards Standard Reference Material (SRM) cylinder gases. The procedure includes specifications and requirements for: (1) preparation of compressed gas samples in cylinders prepared in lots of ten or more of identical concentration with the average concentration for the lot within + or - 1.0 percent relative to the concentration of a specific SRM; (2) tests to verify compressed gas samples stability and within lot homogeneity; (3) simultaneous submission by the gas manufacturer of analysis results to NBS and cylinder gas numbers to USEPA (without analysis results); (4) random selection by USEPA of two cylinders per lot for an USEPA performance audit analysis; (5) submission by USEPA of audit results to NBS, and (6) decision by NBS whether to allow the gas manufacturer to sell the lot of cylinders as CRM. A procedure for CRM for CO in N2 or air is described as Appendix C. Future appendices will be added for other CRM including NO in N2, SO2 in N2, CO2 in N2, and O2 in N2.