What Is Radon?

Radon is a naturally occurring radioactive gas produced when uranium in soil and rock breaks down. It rises through the ground and can collect inside homes, where long-term exposure increases the risk of lung cancer. You can’t see, smell or taste it — testing is the only way to know your level.

Where does radon come from?

Uranium is present in almost all soil and rock. As it decays it produces radium, which in turn decays into radon gas. Radon moves up through the ground and enters buildings through cracks in foundations, construction joints, gaps around pipes, sump pits and crawl spaces.

Because a house is usually slightly lower in air pressure than the soil around it, it can act like a vacuum and draw radon indoors.

Why is radon dangerous?

When you breathe radon, its short-lived decay products can lodge in your lungs and release alpha radiation that damages lung tissue. The EPA estimates radon is the leading cause of lung cancer among non-smokers and the second leading cause overall in the United States.

What is a safe radon level?

There is no known completely safe level, but guidelines tell you when to act:

How do you test for radon?

You can use a short-term test kit (2–90 days), a long-term test (more than 90 days) or a continuous digital monitor that reports levels every hour. Radon levels change with weather, season and ventilation, so continuous monitoring gives a much clearer picture than a single snapshot.