This document gives guidance on the selection and evaluation of compatibility between non-metallic materials for gas cylinders and valves and the gas contents. It is also applicable to tubes, pressure drums and bundles of cylinders. This document covers composite and laminated materials used for gas cylinders. It does not include ceramics, glasses and adhesives. This document considers the influence of the gas in changing the material and mechanical properties (e.g. chemical reaction or change in physical state). The basic properties of the materials, such as mechanical properties required for design purposes (normally available from the materials supplier), are not considered. Other aspects, such as quality of delivered gas, are not considered. The compatibility data given are related to single component gases but can be applicable to gas mixtures. This document does not apply to cryogenic fluids (this is covered in ISO 21010).