ISO 16664:201 describes factors that may influence the composition of pure gases and homogeneous gas mixtures used for calibration purposes. This document only applies to gases or gas mixtures that are within the "utilization period". It provides the following guidelines for the handling and use of calibration gas mixtures:
- storage of calibration gas cylinders;
- calibration gas withdrawal from cylinders;
- transfer of calibration gas from cylinders to the point of calibration.
It also outlines a method of assessing the stability of a gas mixture, taking into account the gas composition uncertainty given on the certificate and the user's measurement uncertainty.