This European Standard describes common principles for pressure testing, commissioning and decommissioning of gas infrastructures as covered by the functional European Standards of the Technical Committee CEN/TC 234, see Annex B. They have been extracted from the detailed codes of practice and operating manuals in the member countries. This European Standard does not cover installation pipework which is covered by EN 1775. 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 European 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 infrastructure. Users of this European Standard should be aware that more detailed national standards and/or code of practice may 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 basic principles. In the event of conflicts in terms of more restrictive requirements in national legislation/regulation with the requirements of this European Standard, the national legislation/regulation should take precedence as illustrated in CEN/TR 13737 (all parts). CEN/TR 13737 (all parts) give: clarification of all legislations/regulations applicable in a member state; if appropriate, more restrictive national requirements; a national contact point for the latest information.