Radon Gas Entry
Air pressure inside your house is usually lower than pressure in the soil around your home's foundation. Because of this difference in pressure, your home acts like a vacuum, drawing radon in through foundation cracks and other openings. Being in constant contact with the ground, a home’s basement is the main entry point for Radon gas. Entry via parts of the basement with exposed earth like sump wells and drains or through the naturally porous concrete foundation of the basement provide radon plenty of efficient means of entering a home.
In very isolated circumstances water and building materials can also add to radon in your home. All ground water contains some radon, although levels vary greatly. As private wells tap ground water, dissolved radon escapes from the water and gets into household air in the course of dishwashing, showering, and other water-using activities. The radon may also enter our bodies through drinking water. Most public water supplies have very low levels of radon, even if the water comes from municipal wells. This is primarily because such wells tend to tap sand and gravel groundwater aquifers with low levels of radon. Public water supplies also stand for a period before they are consumed and some decay of the radon takes place in that time.
Construction materials have not been found to be important source of radon in Illinois. However, it is possible that concrete or brick made from materials with traces of radioactive materials may be significant sources of radiation in some cases.
In the United States, radon gas in soil in the principal source of elevated radon levels in homes.
ILLINOIS - EPA Map of Radon Zones
The purpose of this map is to assist National, State and local organizations to target their resources and to implement radon-resistant building codes. This map is not intended to determine if a home in a given zone should be tested for radon. Homes with elevated levels of radon have been found in all three zones.
All homes should be tested, regardless of zone designation.