Radon is a cancer-causing, radioactive gas that you cannot see, smell or taste. When you breathe air containing radon, you increase your risk of getting lung cancer. It is the second leading cause of lung cancer in the United States today. You cannot predict radon levels. Even homes next to each other can have different levels. Testing is the only way to know.
The US Environmental Protection Agency (EPA) and the Surgeon General recommend testing homes below the third floor for radon. If you find that you have high radon levels, there are ways to fix a radon problem. Even very high levels can be reduced to acceptable levels.