Radon is a naturally occurring radioactive gas that is invisible, odorless, and tasteless. It enters homes and buildings through cracks, crevices, or holes in the structure. It enters directly from the soil, such as in crawlspaces, or from an open sump pump. Radon can accumulate to unsafe levels inside homes and buildings.
Long term exposure to radon has been linked to cancer. Studies have shown radon can increase the chances of lung cancer. The American Lung Association, the American Cancer Society, along with other health organizations and groups estimate over 20,000 deaths occur each year due to radon exposure. The U.S. Environmental Protection Agency (EPA) and the U.S. Surgeon General recommend home testing for radon, as testing is the only way to know if radon is present.
Radon can be a concern for houses that are "tight" or, in other words, houses that have less air changes per hour, which is common in some weatherized homes. Before a home is weatherized, it is recommended that a radon test be completed before any enenrgy efficient retrofits are completed.
For more information on Radon in homes, see: EPA Radon