Radon is a naturally occurring radioactive gas. It is invisible and has no odor or taste. It comes from the normal decay of uranium and thorium. These are two chemical elements that can be found in soil, rock, and groundwater. Radon breaks down quickly, giving off radioactive particles. Over time, breathing in high levels of these particles can cause lung cancer.

Outdoors, there are low levels of radon in the air. But radon can also be indoors. It can enter homes and buildings through cracks in the floors, walls, or foundations. Certain building materials can give off radon. And sometimes radon gets inside through well water.

Radon levels can be higher in homes and buildings that are well insulated, tightly sealed, and/or built on soil that has a lot of uranium and thorium. Basements and first floors usually have the highest radon levels because they are closer to the ground.

When you breathe in radon, its radioactive decay products can get trapped in your lungs. They can damage the cells that line your lungs. Over time, it can lead to lung cancer. It may take years before this happens.

Radon is the second leading cause of lung cancer deaths after cigarette smoking. If you smoke and are exposed to radon, your risk of lung cancer is much higher than if you did not smoke. Most radon-related cancer deaths happen in smokers.

Testing is the only way to know if there are high levels of radon in your home. You should test your home's radon levels:

• If it's never been tested or the radon levels are unknown
• When preparing to buy or sell your house
• Before and after any renovations, especially after making any repairs to reduce radon levels
• Before making any lifestyle changes in the home that would cause someone to spend more time in the basement or lower level (such as converting a basement to a bedroom)

Testing is fairly inexpensive and easy to do. You can buy a test kit at most hardware stores or hire someone to do a test. It's a good idea to first contact a state or local radon official for advice. They can explain the differences between testing devices and recommend the most appropriate test for your needs. They can also give you a list of qualified radon testers.

There are both long- and short-term test kits:

• Short-term kits measure radon for 2-90 days for quick results
• Long-term kits measure radon in your home for over 90 days

Radon levels can vary from day to day and month to month. So a long-term test will give a better estimate of your average radon level.

If the testing shows that you have an unsafe level of radon in your home, you can have a radon reduction system installed. It can bring the amount of radon down to a safe level. The cost of the system will depend on the size and design of your home.

You can also take some other steps to reduce radon levels in your home:

• Increase air flow in your house by opening windows and using fans and vents to circulate air. But this will only temporarily reduce the radon levels.
• Seal cracks in floors and walls with plaster, caulk, or other materials designed for this purpose.
• After any fixes, monitor the radon levels to make sure that they are lower.