This part of ISO 11665 describes radon-222 integrated measurement techniques with passive sampling. It gives indications for determining the average activity concentration of the radon-222 in the air from measurements based on easy-to-use and low-cost passive sampling, and the conditions of use for the sensors.This part of ISO 11665 covers samples taken without interruption over periods varying from a few days to one year.This measurement method is applicable to air samples with radon activity concentrations greater than 5 Bq/m3.