The exhalation of radon from building materials is a serious risk to occupants’ health. This paper studied the indoor radon diffusion under three-dimensional unsteady conditions. The radon exhalation rate of building materials was measured using a radon collection chamber combined with a RAD7-based radon/thoron detector. The indoor radon diffusion under different ventilation patterns were simulated by CFD (Computational fluid dynamics) based on the stabilization of radon concentration after 10 hours in a closed environment as an initial condition. The results show that the stabilization time is 20 minutes, which can be reduced by appropriately increasing the air inlet velocity. Further increase in air velocity from 0.3 m s^-1 did not produce any significant changes in the stabilization time and the average radon concentration. Our findings show that the better way to reduce indoor radon concentration is to have the air supply inlet at the top or upper side and the air return outlet on the lower side of the room. The indoor radon can be reduced to a steady level after 20 minutes using the better ventilation method. The findings would contribute to the control of the indoor radon dispersion, and to alleviate and reduce occupants’ exposure to high radioactive concentration of radon in urban cities.

从建筑材料中呼出don是对乘员健康的严重威胁。本文研究了三维非稳态条件下室内ra的扩散。使用a收集室结合基于RAD7的ra / tho检测器测量建筑材料的ex呼出率。基于CFD（计算流体力学），模拟了在不同通风方式下室内diffusion的扩散，并基于在封闭环境中初始条件下10小时后ra浓度的稳定化。结果表明，稳定时间为20分钟，可以通过适当增加进气速度来减少。空气速度从0.3 ms ^-1进一步增加稳定时间和平均ra浓度没有任何显着变化。我们的发现表明，降低室内ra浓度的更好方法是在房间的顶部或上方设置进气口，在房间的下方设置进气口。使用更好的通风方法，可以在20分钟后将室内reduced降低到稳定水平。这些发现将有助于控制室内ra的扩散，并减轻和减少居住者在城市中暴露于高放射性concentration浓度的情况。