This report outlines the procedures for cleaning industrial-process measurement and control equipment to be used for oxygen service, verifying this cleanliness and ensuring that the cleanliness of the equipment will be maintained up to the stage where the equipment is installed. This report does not apply to measurement and control equipment for welding, which is covered by ISO 5171. Oxygen service is defined as equipment or part thereof being in contact with oxygen-rich gas mixtures and other oxydizing gases (e.g. laughing gas). Greases, oils, thread lubricants, dirt, water, filings, paints, varnishes, scales, powder, etc., shall be removed because many of these materials, in particular oils and hydrocarbon greases, can react violently in the presence of oxygen and initiate fires or explosions. This report consequently covers the cleanliness procedures for the preparation, assembling, inspection, protection during transportation, storage and handling and installation of equipment, accessories or replacement parts intended for oxygen service. NOTE – Many factors can influence the reaction in the presence of oxygen. Those may be: – a higher oxygen pressure; – a higher temperature; – the fact that oxygen flows, or is only present as a static pressure within equipment or part thereof.