Radon
Entry into Homes
Radon is a naturally occurring gas produced by the breakdown of uranium in soil and water. Warm air is less dense than cool air and the air temperature in homes is usually warmer than the soil surrounding the foundation. Therefore, air pressure inside a home is usually lower than in the earth beneath the home. Because of this difference in pressure the home acts like a vacuum, drawing radon in through foundation cracks. Cracks in solid floors, construction joints, cracks in walls, gaps in suspended floors, gaps around service pipes, cavities inside walls, and sumps are all potential entry points.
Although a number of factors can affect radon levels in homes, the predominant driving force is building induced soil suction. Wind, temperature changes, weather fronts/changes in barometric pressure, freezing and thawing of the earth, rainfall and associated rises in the water table, soil type (sand, clay, etc.) can all affect radon movement. Of course, a radon source must be present and the strength of the source is a major factor.
Radon may also enter in well water. For more on radon in water, click here.
In a small number of cases, the building materials can give off radon, although building materials rarely cause radon problems by themselves.