It's hard to know if radon is present in your home in dangerous levels. The gas occurs naturally as uranium and other radioactive materials in rocks and soil break down, and it has no odor or visible sign.

Since the air pressure in a home's foundation is usually lower than the soil pressure, radon will enter the home through cracks and other openings. The Environmental Protection Agency says radon can also be released through water piped into the home. While small levels of radon are generally not cause for concern, elevated levels are dangerous; radon has been named as the second most common cause of lung cancer after smoking.

Testing your home will let you know if your radon levels are high enough that they need to be treated. There are several remediation methods to help bring down radon levels and help improve the safety of your home.

The radon levels in your home should not be higher than four picocuries per liter of air. You can pick up a test kit at a home improvement store to take measurements. Natalie Rodriguez, writing for This Old House, says both long-term and short-term monitoring is available.

If the radon levels in your home are too high, contact your state EPA office to get a list of qualified contractors in your area. National Radon Program Services, a service of the EPA and Kansas State University, recommends asking any contractor you choose for references, proof of insurance, and proof that they have completed a national certification program for radon remediation.

One of the most common ways to lower radon levels is through a soil depressurization system. This method works to collect radon in the soil before it can enter the home and exhaust it into the atmosphere, far enough away from windows or other openings that it won't reenter the residence. The system typically consists of a plastic pipe that runs into the soil and has a continuously running fan to expel the radon gas.

Such systems require some excavation beneath the foundation, but they can sometimes be connected to existing home features. Rick Muscoplat, writing for Family Handyman, says a system that sucks radon out of the soil may establish negative air pressure in an existing sump pump pit. The soil of a crawlspace may be covered over with plastic, with ventilation of the air under this membrane. A system may also be designed to remove radon gas from the openings in block walls.

Any effort to reduce radon in the home should include the sealing of any cracks or gaps in the foundation. While this process alone usually isn't enough to establish safe levels of radon, it can help lower them.

The pipe in a radon remediation system should exhaust gases at least 10 feet above the ground and at least 10 feet away from any windows, doors, or other openings. The Minnesota Department of Health says it should not exhaust in or underneath any livable area.

A U-pipe will be included in the system to help ensure that it is working properly. This indicator will display fluid, which will be higher on one end than the other; if the levels equalize, it means the fan is no longer working or some other problem has stopped the depressurization.

Multiple radon reduction systems may be used together. The EPA says other options include pressurization to blow air into the basement and keep radon from entering the living spaces as well as an air-to-air heat exchanger, which brings in outside air and uses heated or cooled interior air to affect the temperature of the incoming air.

In a soil depressurization system, the fan should be kept constantly running. National Radon Program Services says the energy use required to run this device is about equal to that needed for a 60- to 90-watt light bulb.

Maintenance of a radon reduction system is fairly minimal. The EPA says you should regularly check the U-pipe to make sure the system is in good working order; the fan typically has a lifespan of about five years, after which it will need to be repaired or replaced. If you have an air-to-air heat exchanger, you'll need to periodically clean and change the filters.