This part of ISO 16486 specifies the general properties of unplasticized polyamide (PA-U) compounds for the manufacture of pipes, fittings and valves made from these compounds, intended to be buried and used for the supply of gaseous fuels. It also specifies the test parameters for the test methods to which it refers. ISO 16486 is applicable to PA-U piping systems the components of which are connected by fusion jointing and/or mechanical jointing. This part of ISO 16486 establishes a calculation and design scheme on which to base the maximum operating pressure (MOP) of a PA-U piping system.