Testing is the most important step in preventing radon poisoning. Radon is a cancer-causing gaseous element that results from the natural breakdown of uranium in soil, rock, and water. Testing is the most essential step in keeping you and your family safe from radon because it cannot be seen or smelled. Radon is the second leading cause of lung cancer in the United States. In Colorado, nearly half of homes have high radon levels, and more than 500 lung cancer deaths in the state each year are attributed to radon. The best way to protect against radon is to perform a simple, low-cost test of your home.