ISO/TC 158/WG 2 - Quality assurance of gas analysis

This document provides requirements and guidelines on the necessary quality assurance required to produce calibration gas mixtures that are demonstrably stable and comparable. It shows that this is achieved by demonstrating that the composition of the calibration gas mixture is metrologically traceable to the SI. This document shows that calibration gas mixtures can be prepared according to methods that have measurements that are completely described in SI units. It describes procedures for verifying that the composition of such gas mixtures is correct within the stated measurement uncertainty. Guidance is given as to how to conduct the evaluation of uncertainty in these procedures. This document also shows how a calibration gas mixture with unknown composition can be calibrated by reference to traceable standard gas mixtures. This document covers the commonalities and differences of quality management schemes in use by producers of calibration gas mixtures, most notably those described in ISO/IEC 17025 and ISO 17034. These systems lead to gas mixtures with different characteristics, and this document explains these differences and their implications. Calibration gas mixtures, as prepared and certified for composition in accordance with this document, are used for the calibration of equipment, the performance evaluation of methods, measurement procedures and equipment.

ISO/TS 14167:2003 provides guidance on the quality aspects in the field of gas analysis that are implemented in order to achieve a result with a valid measurement uncertainty. It provides guidelines on quality aspects to be employed in gas analysis using calibration gas mixtures and their subsequent validation and/or verification, and the testing of the analytical performance of gas analysis instruments. These guidelines have the overall objective of defining procedures which will ensure that measurements of gas composition are reliable, comparable and consistent between different organizations and countries. It explains, in particular, the concepts of measurement uncertainty and of traceability as effective quality assurance tools for defining the measurement uncertainty of particular measurement results. It also gives guidance on how to identify and estimate measurement uncertainty components of the result, and how to combine these uncertainty components in order to obtain the overall uncertainty.