Radon Gas Testing and Mitigation

creepy basement
•••  Naomi Armendariz / EyeEm / Getty images

Radon gas is a colorless, odorless, tasteless radioactive gas that's formed during the natural breakdown of uranium in soil, rocks, and water. Radon exits the ground and can seep into your home through cracks and holes in the foundation, as well as contaminate well water. There are no average radon levels for a specific city, state, or region, and houses without basements are as much at risk of radon contamination as houses with basements.

 Health officials have determined that radon gas is a carcinogen that can cause lung cancer, and studies show that radon is more of a risk to smokers, but non-smokers have a slightly elevated chance of developing lung cancer when radon levels in the home are high. The only way to find out if your house contains radon gas is to perform radon tests.

EPA Radon Gas Studies

The Environmental Protection Agency (EPA) recommends you install a system to reduce radon gas in your home if the level of gas is 4 picocuries of radon per liter (pCi/L) or higher. The EPA also offers a look at what they believe to be the risks of radon at different concentrations for 1,000 people who smoked and were consistently exposed to a certain level of radon during their lifetimes.

Radon Risks for Smokers:

  • With exposure to 10 pCi/L, about 71 would get cancer, equal to 100 times the risk of dying in a home fire.
  • With exposure to 4 pCi/L, about 29 would get cancer, equal to 100 times the risk of dying in a plane crash.

Radon Risks for Non-Smokers:

  • With exposure to 8 pCi/L, about three would get cancer, equal to 10 times the risk of dying in a plane crash.
  • With exposure to 4 pCi/L, about two would get cancer, equal to the risk of drowning.

Testing Methods

There are two basic types of radon gas testing devices: passive and active. You can order a radon test kit and set it up yourself, or you can hire a professional to perform the test. Passive testing devices do not need power to function and include charcoal canisters, alpha-track detectors, and charcoal liquid scintillation devices that are exposed to the air in your home for a specific amount of time and then sent to a laboratory for analysis.

Actives devices—which are generally considered to be more reliable than passive radon devices—require power to function and continuously measure and record radon in the air, making radon spikes and dips more apparent. These devices are normally used only by home inspectors and air quality professionals.

Length of Testing

Long-term radon tests take more than 90 days but provide an accurate picture of the average amount of radon in your home. Since time is an issue, homebuyers usually perform short-term radon with either an active or passive testing device. Most short-term radon tests are completed in 48–96 hours.

How to Test

The EPA recommends that you perform radon tests on the lowest level of the home that could be used for living space without doing renovations. Choose a room that is used regularly, but do not use the kitchen, bathroom, laundry room, or a hallway. Keep windows and doors in the tested room shut except for normal entry and exit. For tests lasting less than four days, make sure windows and outside doors are closed for at least 12 hours before beginning. 

Place the testing device at least 20 inches above the floor so that it is out of drafts and high humidity, follow the manufacturer's instructions to record starting and ending times, then reseal the tester package and return it to the lab for analysis once finished. Sometimes two devices are used simultaneously, or two 48-hour tests are done back-to-back to help establish average radon levels and to verify that devices are working properly. While recommended, it is not required. If you use an active device, the tester will give you instructions about what you should and should not do during the test.

High Levels

About 0.4 pCi/L of radon is found in the outside air, and the average indoor radon level is about 1.3 pCi/L. Radon levels can usually be lowered using a process called mitigation. Some radon mitigation methods prevent radon from entering your home, and others reduce radon levels after the gas is there. The EPA recommends you use mitigation techniques to reduce indoor radon if levels in your home are above 4 pCi/L (or 0.02 working levels if your lab uses that reporting method). 

Common Mitigation Methods

  • Soil suction: A mitigation system that draws radon from beneath the house and vents it away from the house through pipes.
  • Sealing cracks and openings: Sealing alone doesn't usually lower radon levels, but it can limit the flow of radon into a home and reduce the loss of air that's been heated or cooled.
  • House pressurization: This method uses a fan to create pressure differences that help keep radon from entering the house.
  • Heat Recovery Ventilator (HRV): Installed to increase ventilation, HRV uses the heated or cooled air being exhausted to warm or cool the incoming air. This type of system is most effective when used to ventilate only the basement of a house.
  • Eliminating it in water: Use this type of system if you've determined that your private water supply is your home's source of radon. Point-of-entry treatments use charcoal filters or aeration devices to remove radon from water before it enters your home, and point-of-use devices remove radon at the tap, but doesn't reduce radon in unfiltered taps—such as your tubs, showers, and laundry areas.

Existing vs. New House

If your house already exists, your radon mitigation contractor can offer complete details about different types of radon reduction systems and which is better for your specific situation. Costs vary, but most systems can be installed for $1,000–$3,000. If you're building a new home, now is the time to install a radon-reduction system. The cost is far less than fitting a system after the home is built, and having the system in place will help the home's resale value. The EPA offers important advice to help you find a qualified radon service professional.

If you are buying a home, be sure to include a radon contingency to your offer to purchase, stating the maximum level of radon that is acceptable to you. If tested levels are above that figure, you should have the right to back out of the contract with no penalties. Many standard forms contain a radon contingency addendum that can be added to your offer to purchase.

Radon Tips for Home Sellers

Test your home for radon before you put it on the market. Use a long-term test if you have the time, but if not, perform at least two short-term tests. You can do the initial test yourself to save money, but homebuyers are more impressed with the test results from a qualified professional. To find out if your state requires specific licensing for radon professionals, refer to the EPA's list of contacts by region.

If radon levels are too high, install a radon-reduction system, and use the EPA's guidelines to help you choose a qualified radon service professional. Keep all installation details to share with your buyer. Low radon levels are a selling point; if you find out now that there's a high amount of radon in your home, you'll have time to decide if you'll participate in a reduction system.

EPA's Radon Video

The EPA offers consumers a video about radon in real estate. Order a free copy by calling the Indoor Air Quality information line, 1-800-438-4318, and asking for publication number. The more you know about radon, the better you will protect you and your family's health.