January is National Radon Action Month. With less than a week left in the month, health agencies and advocacy groups are working together to increase awareness.

Radon is a naturally-occurring, invisible and odorless radioactive gas. The EPA says radon in the leading cause of lung cancer among non-smokers. One out 15 homes contains high levels of the gas, which means millions of Americans are unknowingly being exposed to it. Statistics show that radon caused more deaths than carbon monoxide, fires and guns combined.

The EPA and the Surgeon General are encouraging people to call their state radon offices on finding qualified test kits or testers, especially if their homes haven’t been tested within the last two years.