Modeling radon (222Rn) development in confined environments aids in predicting radon levels in dwellings and underground spaces, where radium 226Ra in building materials and soil emits radon gas via radioactive decay. Radon accumulates in poorly ventilated places, creating an inhalation hazard. In OpenFOAM, a C+ +-based computational tool, an existing heat conduction solver was adapted to simulate radon accumulation, considering radon's radioactive characteristics and material non-uniformity through which radon will permeate. The solver was validated against theoretical values in a one-dimensional system and then applied to study radon dispersion in containment, with potential for broader applications.