This document provides methods for — calibrating an instrument with one or two calibration gas mixtures, — determining the composition of a gas sample, and — evaluating the uncertainty of the composition of the gas sample in relation to the uncertainty of the composition of the calibration gases used and the contribution of the measurement process. This document sets requirements to, and acceptance criteria for, the utilization of different measurement calibration designs with a limited (i.e. minimum) number of calibration gas mixtures used in calibration. The methods in this document are described for amount-of-substance fractions, but are also applicable for other composition quantities (such as mass fractions, volume fractions or concentrations).st edition 2017-04 Gas analysis — Comparison methods for the determination of the composition of gas mixtures based on one- and two-point calibration Analyse des gaz — Méthodes de comparaison pour la détermination de la composition des mélanges de gaz basées sur un ou deux points d’étalonnage Reference number ISO 12963:2017(E) ？ ISO 2017 ISO 12963:2017(E) COPYRIGHT PROTECTED DOCUMENT