Energy conservation intensifies the problem caused by radon in dwellings

Sources of radon and the high levels of radon in many locations and building materials in Sweden are considered. Improvements in energy conservation through the reduction of ventilation rate have lead to very high levels of radon over 1000 BqRnD/m3 in some houses. Recommendations on acceptable levels of gamma radiation on building sites and radon concentration in dwellings are given. It is estimated that there are 30-40,000 dwellings over the Swedish recommended limit of 400 BqRnD/m3 requiring modification.