Intake of radioactivity by inhalation, in buildings after nuclear incidents

Risk studies so far assumed that in case of a nuclear incident, the exposure of persons through inhalation proceeds in free air by direct intake of contaminated ambient air. In reality, however, about 80 p.c. of the population is indoors, and there is a considerable delay of room air contamination in comparison with free air contamination. The radionuclides are deposited on indoor surfaces (such as walls, windows, furniture, etc.), and in air-conditioning systems on the filters. This contamination is somewhat regularly removed through cleaning or filter exchange, which reduces the contamination of room air, and then also the radiation exposure by inhalation. The reducing effect can be enhanced by such simple measures as closing doors and windows in time, and switching the air-conditioning system to recirculating regime, followed by enhanced fresh air supply at a later time. (orig./HP)