This book gives a broad overview of environmental radioactivity, background radiation sources, artificial sources, sources of 222Rn and 220Rn, indoor atmosphere radioactivity, the scope of the current study, and its goals. Additionally, different experimental methodologies were used to measure and analyze spatial variations in the levels of 222Rn, 220Rn, and their progeny in various locations, as well as in houses with various floorings, walls, rooms, and volumes throughout Bangalore Metropolitan, India. In-depth information is presented regarding the volumetric changes in indoor 222Rn, 220Rn, and the distribution of 220Rn and its progeny levels in a home. Some of the findings that are provided here are novel.