This European Standard describes common principles for pressure testing, commissioning and decommissioning of gas supply systems as covered by the European functional standards of the Technical Committee CEN/TC 234 (see Annex B) except for pipework for buildings according to EN 1775. They have been extracted from the detailed codes of practice and operating manuals in the member countries. The specified procedures are applicable to strength testing, tightness testing and combined testing. Test pressure levels, test periods and acceptance criteria are not covered by this standard. Additional measures or different methods of testing, commissioning or decommissioning can be required by legislation of the individual member countries or at the discretion of the pipeline operator. This European Standard specifies common basic principles for gas supply systems. Users of this European Standard should be aware that more detailed national standards and/or codes of practice can exist in the CEN member countries. This European Standard is intended to be applied in association with these national standards and/or codes of practice setting out the above mentioned principles.