COEUR d'ALENE — When Daniel Hunt was house hunting, he noticed "radon mitigation system" on some of the listings as a selling point.

"I didn't even know what radon was," he said.

After the Coeur d'Alene father of four learned radon is a naturally occurring radioactive gas that you can't see, smell or taste — but it can cause lung cancer — he purchased a tester for his home.

When the basement tested for unsafe radon levels under Environmental Protection Agency standards (4 picocuries per liter or higher) and realizing radon rises from the soil invading homes through crawlspaces, foundation cracks and openings, Hunt took immediate action. He opened the basement windows for air circulation until a mitigation specialist arrived.

"It was 7 degrees downstairs," he said. "But I wanted to know that we'd be safe, especially with four kids."

Hunt learned from the specialist that opening his windows in the middle of winter was overkill, but on Wednesday he finally relaxed when a radon mitigation system was installed in his house.

"It's a huge peace of mind," Hunt said.

Areas of Kootenai County have reached as high as 74 percent of homes testing at unsafe levels of radon, according to a report released this week by the Idaho Department of Health and Welfare.

This area remains among the highest in the state for the radioactive gas, said Jim Faust, IDHW radon program manager.

"It's a serious issue throughout the state, but especially in Kootenai County," he said.

Radon is the second-leading cause of lung cancer, according to IDHW. The Environmental Protection Agency estimates radon causes 21,000 deaths in the country each year.

Since the state began compiling data on home tests 16 years ago, 40 percent of the homes statewide have tested at unsafe radon levels.

The percentage of Kootenai County homes that tested at unsafe levels range from 38 to 74 percent, depending on the location. The results can vary greatly even in the same neighborhood and during different times of the year.

Of 13 tests in the Worley area, 38 percent were at unsafe levels. In the Athol/Bayview area, 271 tests have been completed with 74 percent of the homes unsafe.

"Athol is probably one of the worst areas in the country for it," said Dave Gerard, a radon mitigation specialist.

In the Coeur d'Alene/Dalton area with an 83815 zip code, 64 percent of the homes out of 917 were unsafe. In the Coeur d'Alene area with an 83814 zip, 52 percent out of the 640 homes were unsafe.

In Post Falls, two-thirds of 925 homes were deemed unsafe.

Faust said the majority of the Kootenai County numbers were from tests in the past five years as radon awareness has increased.

Gerard said his business has doubled in recent years on radon testing and system installations.

Monte Hilding, a radon specialist, said he waited about a year to install a system in his own home in Rathdrum after it tested at unsafe levels. In hindsight, he said he wishes he wouldn't have waited that long.

"I didn't want to spend money on a system for something I can't see," he said. "But it was something on my worry list that wasn't going away. It all boils down to what people's risk tolerance is. The reality is that not everybody will get sick or cancer from radon, but there is a percentage who will."

What that percentage is remains agonizingly fuzzy, he said

"There's no way to test somebody who is susceptible," Hilding said.

Gerard equated radon mitigation to putting on seat belts. He believes radon tests should be a mandatory part of home inspections, but doesn't believe it ever will be in Idaho.

Geology, he said, is a factor in radon levels as levels are lower in areas north and south of Kootenai County. Porous conditions in the soil caused by the Missoula floods are partially what makes this area prone to radon, he said. Radon comes from the breakdown of uranium in rocks and soil.

The good news, Faust said, is radon problems can be fixed with mitigation.

He believes all homes should be tested because that's the only way to tell how high levels are. Test kits are available at hardware and home improvement stores.

They can also be purchased at www.radonidaho.org with easy-to-follow instructions for $9.95. The shipping and lab analysis costs are included.

Winter is the best time to test for radon. The test should be performed on the lowest floor of your home where you spend time.

If your home tests at unsafe levels, parts to reduce radon range from $300 to $600 if you make the improvements yourself. The cost to have a certified specialist do the work ranges from $1,500 to $2,500. The cost of installing radon-resistant features during construction runs from $300 to $500.

For more information on radon, call (800) 445-8647.