The influence of a controlled natural ventilation on the indoor radon decay products concentration: a case study.

Air exchange rates in occupied buildings are difficult to assess due to their dependence on a multitude of climatic parameters and inhabitant behaviour. Moreover, the assessment of the influence of the air exchange rate on the radon progeny concentration is hampered by the diurnal and seasonal fluctuations of the indoor radon levels. Experiments involving two adjacent rooms submitted to identical conditions influencing the radon concentration and showing similar temporal variations and levels of radon progeny provide a mean to assess the contribution of a controlled natural ventilation enhancement to the reduction of the indoor radon progeny concentration. First results show, that one additional air exchange per day reduces the mean indoor radon progeny concentration by about 5 %. This indicate that natural ventilation is not sufficient to reduce the indoor concentration of radon decay products to an acceptable level in areas with elevated radon source strength, especially during the winter.