Abstract: A method of containing a sample of a gaseous mixture flowing in a pipeline at a flow rate, for analysis of same by at least one analyzer of which the operating conditions are not compatible with the physico-chemical conditions of the gaseous mixture in the pipeline is described. The method includes collecting a sample of the gaseous mixture in the pipeline, diluting the collected sample with a dry dilution gas, at a dilution temperature (T_dil) equal to or close to the temperature (T_prel) of the gaseous mixture in the pipeline during the collection step, and conveying the collected and diluted sample out of the pipeline via an outlet pipe for analysis of the same by said analyzer.