IEC 61577-2:2014 describes the specific requirements for instruments measuring the activity concentration of airborne 222Rn and 220Rn outdoors, in dwellings and in workplaces including underground mines. This standard applies practically to all types of electronic measuring instruments that are based on either spot or continuous measurements. The different types of instrumentation used for measurements are stated in IEC 61577-1. This new edition includes the following significant technical changes with respect to the previous edition: - addition of new requirements and tests concerning performance; - harmonization of the requirements and tests concerning performance with other standards in this area.