Uranium and radium are present in soil, rocks, water and building materials, therefore the presence of 222Rn in the air is natural, and its concentration is determined mainly by physical factors such
Radon-222 (222Rn), formed within the 238U chain by decay of 226Ra, is the main radioactivity source of groundwater. Radon has three radioactive isotopes but only 222Rn is of interest having a half-lif