How Does Radon Get Into Your Home?

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indoor Radon Program How Does Radon Get Into Your Home?Radon is a radioactive gas. It comes from the natural decay of uranium that is found in nearly all soils. It typically moves up through the ground to the air above and into your home through cracks and other holes in the foundation. Your home traps radon inside, where it can build up. ​

Radon levels in homes can fluctuate. Levels can be affected by a number of factors, including weather, soil moisture, and air pressure. Differences in the air pressure inside the home compared to air pressure outside of the home can create a vacuum, called an air pressure differential, which draws radon into the home. Normal activities such as using the furnace, the bathroom fan, a whole house fan, or the clothes dryer will pull air into the house which contributes to air pressure differentials. Because of this fluctuation, it is best to test your home in the winter months, when radon levels typically are higher.

Nearly 1 out of every 15 homes in the U.S. is estimated to have elevated radon levels. Elevated levels of radon gas have been found in homes throughout California. While radon problems may be more common in some areas, any home may have a problem. You cannot predict which homes will have high radon levels. Two identical homes on the same street can have different radon levels. The only way to know a building's radon level is to test.  

Radon has been found in all types of homes, including:

  • Old homes
  • Well sealed homes
  • Drafty homes
  • Homes with basements
  • Homes built on slabs
  • Homes with crawl spaces

Radon and Building Materials

Some natural building materials, such as granite, stone and some concrete products, can give off very small amounts of radon. However, building materials rarely cause radon problems by themselves. Radon gas in soils is the primary source of radon in homes. If your home has natural building products, including granite countertops, it will generally not contribute a significant amount of radon to the air in your home. If you still wish to test your granite countertops or other material, there are specific granite test kits you can purchase from test kit manufacturers. Handheld meters are not recommended. To reduce your radon risk you should first test the air in your home to determine the radon level.

Any home may have a radon problem. The only way to know is to test.

  • Radon Testing Page

  • Radon Program

  • USGS Report "Geology of Radon" (PDF)

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