Out of more than 300 entries, the Colorado Department of Public Health and Environment has chosen three student winners for its radon poster contest.

Hunter and Asher of Windsor Middle School took first and second place, with prizes of $300 and $200, respectively. Addison, a student at Columbine Middle School in Montrose, took third place and will receive $100. The department did not provide last names of the winners.

Each student’s teacher will also receive a $100 gift card.

“This contest is a fun way to educate children and encourage residents to test their homes for radon,” said Chrystine Kelley, the radon program manager for CDPHE. “Radon testing is easy to do, and it’s the only sure way to tell whether or not your home is affected by radon, which occurs naturally in the soil.”

The first place winner will have the poster appear on the state’s radon information site through 2020, and it will also be entered into the U.S. Environmental Protection Agency’s national contest.

Radon is a colorless, odorless gas that derives from the uranium in rock, soil, and water. Once it leaves the earth, radon can get trapped inside homes, creating a lung-cancer hazard.

In San Juan County, nearly 90% of tested homes registered hazardous levels of radon. CDPHE reports that all 64 Colorado counties are at high risk of radon in the home.