This International Standard provides methods for determining the composition of a calibration gas mixture by comparison with appropriate reference gas mixtures, calculating the uncertainty of the composition of a calibration gas mixture in relation to the known uncertainty of the composition of the reference gas mixtures with which it was compared, checking the composition attributed to a calibration gas mixture by comparison with appropriate reference gas mixtures, comparing the composition of several calibration gas mixtures, e.g. for the purpose of comparing differentmethods of gas mixture preparation, or for testing consistency among gas mixtures of clo