[Role of the number of stories in the radiation-sanitary assessment of residential buildings].

Upon long-term exposure, the radioactive gas radon-222 and its decay products in increased doses adversely affect human health. Since the human being spends about 65% of his time in the buildings, it is necessary to evaluate air radiation purity in the rooms, which can be obtained by making a sanitary radiological survey of residential buildings. The scope of the rooms in many-storeyed buildings to be examined can be considerably reduced if the regularities in radon distribution are known. This paper deals with searches for regularities in the distribution of radon levels by the floors of many-storeyed buildings in Tomsk. The room air concentrations of radon were measured for 18 residential buildings with tract detectors upon 1-3--month exposure. The findings showed a different pattern in the distribution of radon levels by the floors in relation to the structural features of a building and to the type of a building material. The wooden and slag-concrete buildings show a 2-3--fold increase in radon levels on the lower floors as compared to the upper ones. A statistical analysis of measurements in the bearing-wall and brick buildings revealed no association of the concentration of radon with the level of a floor, the distribution is near-uniform with 15-30% standard deviation, which is within the limits of measurement error.