This document gives guidance in the selection and evaluation of compatibility between non-metallic materials for gas cylinders and valves and the gas contents. It also covers bundles, tubes and pressure drums. This document can be helpful for composite and laminated materials used for gas cylinders. It does not cover the subject completely and is intended to give guidance only in evaluating the compatibility of gas/material combinations. Only the influence of the gas in changing the material and mechanical properties is considered (for example chemical reaction or change in physical state). The basic properties of the materials, such as mechanical properties, required for design purposes are normally available from the materials supplier and are not considered in this document. The compatibility data given are related to single component gases but can be used to some extent for gas mixtures. Ceramics, glasses, and adhesives are not covered by this document. Other aspects such as quality of delivered gas are not considered. This document is not intended to be used for cryogenic fluids (see ISO 21010).