This International Standard specifies requirements for certificates for pure gases and for certificates for homogene-ous 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 underpressure in a cylinder or other container. This International Standard does not cover the field of safety-relevant data and re-lated 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.