What Is Radon, and Should You Test Your Home?
Radon is a radioactive gas that forms naturally when uranium, thorium or radium break down in rocks, soil and groundwater, the EPA says, and people are exposed mainly by breathing radon in air that comes through cracks and gaps in buildings and homes. The EPA says radon is the second leading cause of lung cancer overall and is responsible for about 21,000 lung cancer deaths every year, about 2,900 of them among people who have never smoked.
There is usually no early warning. The CDC says that when you breathe in radon, radioactive particles from its decay can get trapped in your lungs, that lung cancer takes many years to develop, and that most people do not have symptoms until lung cancer is advanced, when it is harder to treat.
The EPA says the quickest way to test is with a short-term test, which stays in the home from two to 90 days depending on the device, while a long-term test stays for more than 90 days and is more likely to show the home’s year-round average level. It recommends fixing a home if the radon level is 4 pCi/L (picocuries per liter) or more, and because there is no known safe level of exposure to radon, it also recommends considering fixing homes with levels between 2 and 4 pCi/L.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Government sourceThe EPA says radon is a radioactive gas that forms naturally when uranium, thorium or radium break down in rocks, soil and groundwater, and that people are exposed mainly by breathing radon that comes through cracks and gaps in buildings. US EPA ↗
- Government sourceThe EPA says radon is the second leading cause of lung cancer, responsible for about 21,000 lung cancer deaths every year, about 2,900 of them among people who have never smoked. US EPA ↗
- Government sourceThe EPA recommends fixing homes with radon levels of 4 pCi/L or more, and because there is no known safe level of exposure, recommends considering fixing homes with levels between 2 and 4 pCi/L. US EPA ↗
- Government sourceThe EPA says the quickest way to test is with a short-term test, which remains in the home from two to 90 days depending on the device. US EPA, Home Buyer’s and Seller’s Guide to Radon ↗
- Government sourceThe EPA says long-term radon tests remain in the home for more than 90 days and are more likely than a short-term test to show the home’s year-round average level. US EPA, Home Buyer’s and Seller’s Guide to Radon ↗
- Government sourceThe CDC says radioactive particles from radon can get trapped in the lungs, that lung cancer takes many years to develop, and that most people do not have symptoms until it is advanced. CDC ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.