This International Standard specifies requirements for the oxygen compatibility of materials, components and devices for anaesthetic and respiratory applications, which can come into contact with oxygen in normal condition or in single fault condition at gas pressures greater than 50 kPa. Additionally, this International Standard gives general guidelines for the selection of materials and components based on available data on their oxygen compatibility, and for carrying out a risk analysis, including addressing the toxicity of products of combustion and/or decomposition. Aspects of compatibility that are addressed by this International Standard include cleanliness, resistance to ignition and the toxicity of products of combustion and/or decomposition at the design, manufacturing, maintenance and disposal stages. This International Standard does not apply to biocompatibility. This International Standard is applicable to anaesthetic and respiratory equipment that is within the scope of ISO/TC 121, e.g. medical gas pipeline systems, pressure regulators, terminal units, medical supply units, flexible connections, flow-metering devices, anaesthetic workstations and lung ventilators.