Like carbon monoxide, you can't see, smell or taste radon, but the gas may be a problem in your home.

It results from disintegrating uranium in the earth - soil, rock and water. Although radon can be found all over the United States, it is especially prevalent in the Rockies, the Midwest and New England. It can get into any type of building - home, office, school - and result in a high indoor radon level.

However, most people are likely to get the greatest exposure at home, where they spend most of their time. It typically makes its way into homes through cracks in concrete floors or basement walls and floors, gaps in suspended floors, gaps around service pipes and cavities inside walls.

According to the Environmental Protection Agency, radon is estimated to cause about 21,000 lung cancer deaths per year. What's more, if you smoke and your home has high radon levels, your risk of lung cancer is especially high.

Nearly one out of every 15 homes in the United States is estimated to have elevated radon levels.

Is radon present in your home? The only means to determine if radon is present and to what extent is through testing. Fortunately, testing is inexpensive, easy and should only take a few minutes of your time. Low-cost do-it-yourself radon test kits can be found at many hardware stores or home centers or can be obtained through the mail.

If you are buying or selling a home or you don't chose to perform the test yourself, you can hire a qualified testing firm. Contact your state radon office for a list of qualified testers.

There are two general ways of testing for radon: short-term and long-term testing. As the name implies, short-term testing is the quickest way to test. The collection device - a charcoal canister or other type of system - remains in your home for two to 90 days.

Since radon levels can vary from day to day and season to season, a short-term test is not likely to produce a reliable year-round average level. A long-term test remains in your home for more than 90 days.

The EPA recommends the following testing steps:

Take a short-term test. If the result is four picocuries per liter of air or higher, take a follow-up test to be sure.

Follow up with either a long-term test or a second short-term test. For a better understanding of your year-round average, take a long-term test. If you need results quickly, take a second short-term test.

If tests demonstrate that your home contains levels of radon that are equal to are greater than four picocuries per liter of air, you should take action to reduce the levels. There are many methods of reducing radon levels. In general, all mitigation methods include some form of sealing or ventilation.

In addition, some techniques prevent radon from entering your home while others reduce radon levels after it has entered. Among the most effective preventive methods is to patch cracks and gaps using caulking and various other types of patching compounds.

Another method, "soil suction," prevents radon from entering your home by drawing it from below the house and venting it through a pipe (or pipes) to the air about the house where it is quickly diluted.

Some methods are "passive" and simply depend on natural ventilation while other "active" methods involve the use of a powered exhaust fan, which should run continuously.

An effective method to reduce radon levels in homes with a crawlspace involves covering the earth with a high-density plastic sheet. A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors.

Higher levels may require more complex measures. If such is the case, the EPA recommends hiring a qualified radon mitigation contractor. Begin by checking with your state radon office. Many states require radon mitigation professionals to be licensed, certified or registered.

If you choose to perform the work yourself, get information on appropriate training courses and copies of EPA's technical guidance documents from your state radon office.

The good news is that radon reduction systems have proven to be effective. In fact, some systems can reduce radon levels by up to 99 percent. The cost for repairs necessary to reduce radon ranges from about $800 to $2500 (with an average cost of $1200) depending upon the size and design of your home and which radon reduction methods are required.

For more information on radon testing and mitigation, visit www.epa.gov/radon or call (800) 557-2366.