An unusual case of indoor air radon contamination: An unusual method for effective mitigation

In the course of routine surveillance for indoor radon in Austria, concentrations above 10,000 Bq/m3 were found in a house in the province of Carinthia, Austria. Multiple 3-day-measurements in all the rooms of the house were carried out for the next 21 months. All rooms of the house had elevated radon concentrations but radon levels decreased systematically from east to west within the house. Moreover, radon concentrations in one room of the building were found to be below 300 Bq/m3 in winter but above 12,000 Bq/m3 in summer. After installing a medium sized fan, operated only during the summer season, the semiannual summer radon levels dropped from approximately 8,000 Bq/m3 to 250 Bq/m3 at ground floor level.