IEC 61207-3:2019 is available as IEC 61207-3:2019 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition. IEC 61207-3:2019 applies to the three main methods for measuring oxygen by its paramagnetic property, which are outlined in the introduction. It considers essential ancillary units and applies to analyzers installed indoors and outdoors. Safety-critical applications can require additional requirements from system and analyzer specifications not covered in this document. This document is intended: - to specify terminology and definitions related to the functional performance of paramagnetic gas analyzers for the measurement of oxygen in a source gas; - to unify methods used in making and verifying statements on the functional performance of such analyzers; - to specify what tests are performed to determine the functional performance and how such tests are carried out; - to provide basic documents to support the application of internationally recognized quality management standards. This third edition cancels and replaces the second edition published in 2002. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) all references (normative and informative) have been updated, deleted or added to as appropriate; b) all the terms, descriptions and definitions relating to the document have been updated where appropriate; c) all references to “errors” have been replaced by “uncertainties” and appropriate updated definitions applied.