[en] Measurements in which electrostatic precipitators have been compared with filter papers for collection of air-borne radioactivity as to the accuracy in alpha and beta measurements have been made. The results show that the filter paper method is as good as the electrostatic method in determining beta-activity disregarding clogging and moisture sensitivity of the filter paper but it is inferior for alpha measurements. Experimental values of the alpha absorption factor for different types of filter papers are given