This document specifies the physical and mechanical properties of pipes made from unplasticized polyamide (PA-U) in accordance with ISO 16486-1, intended to be buried and used for the supply of gaseous fuels. NOTE Additional information about the suitability of PA-U pipe systems for hydrogen and its admixtures is given in ISO 16486-1:2023, Annex D. It also specifies the test parameters for the test methods to which it refers. The ISO 16486 series of standards is applicable to PA-U piping systems, the components of which are connected by fusion jointing and/or mechanical jointing. In addition, this document lays down dimensional characteristics and requirements for the marking of pipes. Pipes conforming to this document are jointed typically by using mechanical, electrofusion or butt fusión techniques.