This International Standard sets forth performance-based criteria and recommendations for the design and use of systems for sampling of airborne radioactive materials in the effluent air from the ducts and stacks of nuclear facilities. The requirements and recommendations of this International Standard are aimed at sampling that is conducted for regulatory compliance and system control. If existing air-sampling systems are not designed to the performance requirements and recommendations of this International Standard, an evaluation of the performance of the system is advised. If deficiencies are discovered, a determination of whether or not a retrofit is needed and practicable is recommended. It can be impossible to meet the requirements of this International Standard in all conditions with a sampling system designed for normal operations only. Under off-normal conditions, the criteria or recommendations of this International Standard still apply; however, for accident conditions, special or separate accident air sampling systems can be necessary.