Being a gas, radon easily can find its way out of rocks and soils, mix with other soil gases and enter homes and other buildings through cracks and openings in foundations.
Some radon can also enter homes through drinking water supplies.
Radon can then enter the air after leaving the water during showering, cooking, and other water use activities. Water from private wells may contain much higher levels of radon than public wells. It is important to note that radon from soil gas is the primary source of radon in most homes. All homes and buildings contain some levels of radon. Radon concentrations can even be detected in outdoor air.