The EPA lists the following ways that radon can get into buildings:

• Cracks in solid floors and walls
• Construction joints
• Gaps in suspended floors
• Gaps around service pipes
• Cavities inside walls
• The water supply

Radon in Soil

Radon gets into the indoor air primarily through pores and cracks in the soil under homes and other buildings.  Usually, the air pressure in homes and buildings is lower than the pressure outside in the soil around or underneath the foundation.  The pressure difference will create suction.  Radon will come through cracks due to that suction (even at lower levels).

Radon in Water

Radon gas can be present in water that comes into your home.  Radon is not a concern if the source of the water is from lakes, rivers, and reservoirs.  In those cases, the radon is mostly released into the air before it enters your home.  There may be a concern when your home’s water supply is from underground sources (groundwater), such as wells.  For those instances, radon can escape from the water during everyday activities such as drinking, washing dishes, cooking and showering.  These actions could make a small contribution to the radon gas present in the air in your home.