This International Standard specifies requirements for certificates for pure gases and for certificates for homogeneous gas mixtures to be used as calibration gases. This International Standard specifies the minimum information (mandatory data) required and additional information (optional data) recommended for characterizing a pure gas, or a homogeneous gas mixture, supplied under pressure in a cylinder or other container. This International Standard does not cover the field of safety-relevant data and related labelling. Two different formats are considered for the information specified by this International Standard: — a certificate, i.e., a document uniquely related to the container; and — a certificate extract, i.e., a document affixed to the container.