This part of EN 1555 specifies the general aspects of polyethylene (PE) piping systems in the field of the supply of gaseous fuels. It also specifies the test parameters for the test methods referred to in this standard. In conjunction with Parts 2 to 5 of EN 1555 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 1); b) an operating temperature of 20 °C as reference temperature. NOTE 1 For other operating temperatures, derating coefficients should be used, see EN 1555-5 [6]. 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.