This document specifies materials and the general aspects of polyethylene (PE) piping systems in the field of the supply of gaseous fuels. NOTE For the purpose of this document the term gaseous fuels include for example natural gas, methane, butane, propane, hydrogen, manufactured gas, biogas, and mixtures of these gases. It also specifies the test parameters for the test methods referred to in this document. In conjunction with EN 1555-2, EN 1555-3, EN 1555-4 and EN 1555-5, this document 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 bar1 at a design reference temperature of 20 °C; b) an operating temperature between "20 °C and 40 °C. For operating temperatures between 20 °C and 40 °C, derating coefficients are defined in EN 1555-5. The EN 1555 series covers a range of MOPs and gives requirements concerning colours. 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 guidance or regulations and installation practices or codes.