It can be found in any home, under any circustances. Radon is an invisible radioactive gas that has no taste, smell or color. Over time, the uranium in rocks and soil decays and radon gas is released. The gas lets off radioactive particles. Because radon is a gas, it can enter buildings through openings or cracks in the foundation. The radon gas itself decays into radioactive solids, called radon daughters or radon progeny. The radon progeny attach to dust particles in the air and can be inhaled.