Fundamental research on the reduction of indoor radon concentration

测定了室内氡（^<222>Rn）浓度，以了解木屋内氡的行为。测量的房屋数量为28栋，分布在从北海道到鹿儿岛的广阔地区。这项测量已经进行了一到三年。木质房屋的氡浓度为3 ~ 22 Bq/m^3，钢筋混凝土房屋的氡浓度为25 ~ 46 Bq/m^3，约为木质房屋的1.5倍。在钢筋混凝土建筑物中，氡浓度在21至1116 Bq/m^3的范围内变化。氡浓度高是由于许多无机材料散发出氡，以及小通风量的影响。从春季到夏季，钢筋混凝土建筑物和木质房屋地板下的氡浓度较高。很明显，从地板下的土壤中散发出来的氡进入了木制房屋。因此，可以通过用混凝土或乙烯基板覆盖木制房屋地板下的地面来减少氡的排放。在未来，日本的木质房屋将成为密闭的，无机材料的使用将会更多，那么此时的氡浓度将比现在的钢筋混凝土建筑要大。

Indoor radon ( ^<222>Rn) concentrations were measured so as to understand the behavior of radon in wooden houses. The number of measured houses was 28 buildings which were located over a wide region from Hokkaido to Kagoshima. The measurement had been carried out for one to three years.The radon concentrations in wooden houses ranged from 3 to 22 Bq/m^3, and those in reinforced concrete houses were from 25 to 46 Bq/m^3 which were about 1.5 times as much as those in the wooden houses. In reinforced concrete buildings, the radon concentrations varied over a range of 21 to 1116 Bq/m^3. The large concentrations are due to radon emanation from many inorganic materials, and from the effect of small ventilation rates. In reinforced concrete buildings and under the floor of wooden houses, the radon concentrations were large from spring to summer. It was made clear that radon emanating from the soil under the floors enters the wooden houses. Therefore, the radon emanation could be reduced by covering the ground under the floors of the wooden houses with concrete or vinyl sheet.In the future, the wooden houses in Japan will become airtight one and the inorganic materials will be used much more, then the radon concentrations will be larger than nowadays like in the reinforced concrete buildings at this time.