This document gives guidance for the assessment of conformity of compounds, products, joints and assemblies in accordance with the applicable part(s) of EN 1555 intended to be included in the manufacturer’s quality plan as part of the quality management system and for the establishment of certification procedures. This document gives recommendations that the quality management system conforms to or is no less stringent than the relevant requirements to EN ISO 9001. NOTE 1 – If certification is involved, the certification and inspection body is preferably compliant with EN ISO/IEC 17065, EN IS0/IEC 17021 or EN ISO/IEC 17020, as applicable. In conjunction with Parts 1 to 5 of EN 1555 (see Foreword), this document is applicable to polyethylene (PE) plastics piping systems for the supply of gaseous fuels. It is applicable to PE pipes, fittings, and valves, their joints and to joints with components of other materials intended to be used under the following conditions: a) a maximum operating pressure, MOP, up to and including 10 bar; b) an operating temperature of 20 °C as reference temperature. NOTE 2 – For other operating temperatures, derating coefficients can be used; see EN 1555-5.