This International Standard covers integrated measurement techniques for radon-220 with passive sampling only. It provides information on measuring the average activity concentration of radon-220 in the air, based on easy-to-use and low-cost passive sampling, and the conditions of use for the measuring devices.This International Standard covers samples taken without interruption over periods varying from a few months to one year.This type of measurement is also applicable for determination of radon-222 activity concentration.