As the still-surging COVID-19 pandemic forces people to remain home five months after the first official stay-at-home orders went into effect, the Colorado Department of Public Health and Environment is urging people to test their homes for radon.

“Testing your home for radon is simple and inexpensive,” said Chrystine Kelley, the department’s radon program manager. “CDPHE also has a low-income radon mitigation assistance program for homeowners that can pay for your radon mitigation system if you qualify.”

Radon is a colorless, odorless radioactive gas found in the earth. Behind smoking, it is a leading cause of lung cancer. While the U.S. Environmental Protection Agency explains that exposure outdoors is not typically a problem because the gas disperses, homes and other buildings can trap radon.

Cherie Summa, the CEO of St. Louis Radon Test and Mitigation in Missouri, said that with school districts pushing learning online for the fall, “children and adults will be spending the majority of their time cooped up in their homes. Radon is responsible for an estimated 21,000 lung cancer deaths per year, and children and pets are at greater risk because of their higher respiratory rates.”

CDPHE added that half of homes in Colorado have radon levels in excess of the EPA’s recommendations. The department has a list of resources for people interested in testing their homes.