This European standard describes specific functional recommendations for the renovation of pipeworks existing in gas supply systems and includes some requirements for materials other than plastics covered by CEN/TC 155 "Plastics piping and ducting systems“. This European standard is intended to be applied in association with EN 12007-1. This European Standard does not apply to pipework in above ground installations. 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 basic principles.