Radon Daughter Concentrations in and Around Dwellings in the Northern Part of the Netherlands

Abstract

The concentration of radon daughters in and around 80 dwellings located in the northern part of the Netherlands has been determined using a one-filter method. Median values of 2.0 and 0.4 mWL were measured for the indoor and outdoor concentrations, respectively. The average outdoor concentration was about an order of magnitude higher for wind directions between SE-SW than from SW-NW. On average, dwellings with double pane windows and/or concrete floors were found to have significantly higher radon concentrations than those with single pane windows and/or wooden floors. For the living room of a particluar dwelling, 18 measurements were carried out. The data for this dwelling indicate a linear relation between the concentration indoors and outdoors with a slope of 3.8 ± 2.0. This unexpected behaviour is thought to be related to ventilation via the crawl space. Measurements of ventilation patterns and measurements of radon concentrations in the living room and the crawl space are consistent with this picture.