MADISON, Wis. -- Every year, more than 175,000 Americans are diagnosed with lung cancer. Of those cases, health officials said that about 10 percent are thought to have been caused by prolonged exposure to radon.

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Officials said that radon exposure can happen without any warning and occur in people's homes, WISC-TV reported.

Like many of the symptoms of lung cancer, radon is silent and undetectable on the surface. It's a colorless and odorless gas that naturally occurs in our environment. However, when radon makes its way into a house's basement, problems can begin. It's known to cause lung cancer, asthma, and emphysema.

Denny Kruger said that he knows all too well how deadly respiratory diseases can be.

"I've got two parents, an older bother, and two older sisters who have all died from emphysema, related to cigarette smoking," Kruger said.

This is why Kruger doesn't smoke, and he said he's doing all he can to help others avoid respiratory issues in their lives. A retired sergeant in the Wisconsin State Patrol, Kruger is spending his retirement as a home inspector. The one thing that he makes sure to test for in every home is excess levels of radon.

"It's the second leading cause of lung cancer in the country," Kruger said. "And the federal government attributes 21,000 deaths a year to exposure to radon."

Radon is a naturally occurring gas, caused by decaying uranium in the earth. Normally, radon makes its way to the surface and quickly dissipates. But it can also enter into basements, where it concentrates and can cause serious health problems.

Radon is measured in picoCuries per liter (pCi/L). A reading of 4 or lower is considered safe. The Dane County average is about 4.96 pCi/L -- a slightly higher reading than what's usually OK. In 2006, a Madison home tested about 180 pCi/L, which is 45 times higher than the safe level, WISC-TV reported.

Radon levels can vary from home to home, and when a homeowner determines they need to do something about high levels, experts like Shane Sparby are working to working to fix the problem. Sparby works for Zander Solutions of Verona, which is one of only a handful of area companies that can get rid of radon in homes.

A radon mitigation system in home is, in essence, a fan and pipes, WISC-TV reported.

"(The fan) is every ounce of what a radon system is," Sparby said. "The rest of it, obviously, is piping, but this is the main component that has to be watched."

The fan acts like a vacuum and draws out radon from the home's foundation, either through holes drilled in the floor or through a sump-barrel. Most systems have a "U-Tube" to let residents know that it's working.

An entire radon mitigation system will cost between $800 and $1,100. Experts like Sparby and Kruger said that it's money well spent in a home with a radon problem.

"It's kind of like driving a car," Kruger said. "You get in a car and you buckle your seat belt. You just don't put yourself in that situation."

Related Info::

Map of Radon levels throughout the state of Wisconsin, searchable by zip code.
Radon Information For Wisconsin Residents