Thoron (Rn-220) is a radioactive gas which is present in our indoor environment. Long-term inhalation of short-lived decay products of thoron may produce radiological effects on human health. The reliable assessment of radiation dose due to inhaled thoron and its decay products requires knowledge about its distribution pattern and concentration levels in an indoor environment. Indoor concentration levels and dispersion of radioactive nuclides mainly influenced by magnitude of source of thoron and turbulent effect due to different living conditions. The present study includes the Finite Volume Method (FVM) for CFD simulations to study the dispersion pattern of indoor thoron gas. The physical problem involves incompressible indoor airflow with fixed position of inlet and outlets. Fluidyn-MP 5.2.1 is general-purpose Multi-Physics software which is used for modeling and simulation purpose. CFD simulation results show a significant effect of different occupation conditions on indoor thoron gas dispersion patterns.