This part of EN 1555 specifies requirements of fitness for purpose of the polyethylene (PE) piping system in the field of the supply of gaseous fuels. It specifies the definitions of electrofusion, butt fusion and mechanical joints. It specifies the method of preparation of test piece joints, and the tests to be carried out on these joints for assessing the fitness for purpose of the system under normal and extreme conditions. It specifies the test parameters for the test methods referred to in this standard. In conjunction with Parts 1 to 4 of EN 1555, it is applicable to PE pipes, fittings, 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 1); b) an operating temperature of 20 °C as reference temperature. NOTE 1 For other operating temperatures, derating coefficients should be used, see Annex A. EN 1555 (all parts) covers a range of maximum operating pressures and gives requirements concerning colours and additives. NOTE 2 It is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects, taking into account their particular requirements and any relevant national regulations and installation practices or codes.