Indoor radon is a serious health concern and contributes about 10% of deaths from lung cancer in the USA and Europe. In this study, radon and thoron levels of 20 multi-floor buildings on the campus of Isfahan University of Medical Sciences were measured in cold and hot seasons of a year. SARAD- RTM1688 radon and thoron monitor was used for measurement. The annual effective dose of radon exposure was also estimated for residences on the campus. The results showed that radon concentration was below the WHO guideline (100 Bq m^− 3) in most of the buildings. The ranges of radon were from 3 ± 10% to 322 ± 15% Bq m^− 3 in winter and from below the detectable level to 145 ± 8% Bq m^− 3 in summer. Mostly, the radon concentration in the basement or ground floors was higher than upper floors, however, exceptions were observed in some locations. For thoron, no special trends were observed, and in the majority of buildings, its concentration was below the detectable level. However, in a few locations besides radon, thoron was also measured at a high level during both seasons. The average annual effective dose via radon exposure was estimated to be 0.261 ± 0.339 mSv y^− 1. The mean excess lung cancer risk (ELCR) was estimated to be 0.10%. It was concluded that indoor air ventilation, buildings’ flooring and construction materials, along with the geological structure of the ground could be the factors influencing the radon concentration inside the buildings. Thus, some applicable radon prevention and mitigation techniques were suggested.

室内氡气是一个严重的健康问题，在美国和欧洲，约 10% 的肺癌死亡是由室内氡气造成的。在这项研究中，测量了伊斯法罕医科大学校园内 20 栋多层建筑在一年中冷热季节的氡气和钍气水平。使用SARAD-RTM1688氡气和钍气监测仪进行测量。还估算了校园内住宅的年有效氡暴露剂量。结果显示，大多数建筑物的氡气浓度低于世界卫生组织的指导值（100 Bq m ^{− 3 ）。}冬季氡气范围为3±10%至322±15%Bq m ^-3，夏季氡气范围为低于可检测水平至145±8%Bq m ^-3。大多数情况下，地下室或底层的氡气浓度高于上层，但也有一些地方存在例外情况。对于钍气，没有观察到特殊趋势，并且在大多数建筑物中，其浓度低于可检测水平。然而，在两个季节中，除了氡气之外，在一些地点，钍气也被检测到处于高水平。氡暴露造成的平均年有效剂量估计为 0.261 ± 0.339 mSv y ^{− 1}。平均肺癌额外风险 (ELCR) 估计为 0.10%。结果表明，室内空气通风、建筑物地板和建筑材料以及地面地质结构可能是影响建筑物内氡浓度的因素。因此，提出了一些适用的氡气防治技术。