Radon is a colorless, odorless radioactive gas that forms as a result of the natural decay of uranium underground. This Radon Information Sheet (PDF) explains more. 

According to the EPA, radon is the number one cause of lung cancer among non-smokers.

The only way to know if your home has high radon is to test. Free test kits are available to City of Aspen residents by filling out this online mail order form. After you submit a mail order form, a kit will be mailed to your home. Kits are NOT available for pick-up through the City of Aspen offices.