Semi-empirical modeling of the temporal variation of indoor radon concentration over short periods

Abstract

The time rate of change of the indoor radon concentration is studied in a semi-empirical frame. The differential equation that describes the radon mass-balance inside a room is used, with taking into account all sources of indoor radon. Rather than solving the equation numerically, an analytical form is obtained with applying some approximations that are based on experimental observations. This makes the describing model more realistic and updatable. After fitting some of the parameters to the experimental data, the model is found to be successful for describing the indoor radon concentration over a couple of days. Moreover, the model predicts some important characteristics of the radon flow to the indoors from the soil and from the building materials. For the room considered in this study, it is found that the radon diffusion transfer coefficient inside the building material is 2.06×〖10〗^(-6) m/h, while the radon diffusion and advection transfer coefficients inside the soil are 0.91×〖10〗^(-4) m/h and 1.04×〖10〗^(-3) m/(h.Pa), respectively. The model can also predict the amount of contribution to the indoor radon by any sources that may be unknown. It was found to be 30.61 Bq/(m^3.h). The obtained results show the feasibility and convenience of the model.