Here’s What Potential Buyers Need to Know About Radon in Homes

Is it a bad idea to buy a home that has high levels of radon? Learn how to test for radon in homes, and how to mitigate the gas safely.

By Glenda Taylor and Bob Vila | Updated Feb 4, 2022 10:56 AM

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radon in homes


Purchasing a new home can be as stressful as it is exciting. In addition to choosing a house that suits your budget and lifestyle, it also needs to be in good structural condition and harbor no hazards—such as high levels of radon gas.

You can’t see it, smell it, or taste it, but radon gas is a leading cause of lung cancer, according to the National Cancer Institute. That doesn’t mean that the presence of radon in homes is a deal breaker, however. Read on to learn all about radon gas: how to have a property inspected for it, why radon in homes is something to be concerned about, and what can be done to remove radon gas from your home to make it safer for your family.

What is radon gas?

Radon gas is a byproduct of the underground decay of radioactive elements, such as uranium and thorium. As these substances deteriorate, the gas is released and eventually works its way to the surface of the ground and into the air we breathe.

Fortunately, radon gas is so diluted in our outdoor environment that it doesn’t pose a health risk. In buildings, however, it can become concentrated. Every state in the U.S. has radon gas, but some areas are a higher risk than others. Check out this interactive EPA map to find out if you’re house hunting in a high-risk zone.

radon in homes


Why should I be concerned about radon?

While radon is considered harmless in the low levels that are found outdoors, when it seeps into a home it can become concentrated in levels high enough to put residents at risk. Radon gas is measured in picocuries per liter (pCi/L), and the EPA recommends radon mitigation for all homes with radon gas levels of 4 pCi/L or higher.

Radon gas is slightly heavier than air, so while it settles in basements and crawl spaces, whole-house HVAC systems have a tendency to distribute the gas throughout the entire home. That means even a second story could potentially contain high levels of radon.

According to the National Cancer Institute (NCI), airborne radon particles are radioactive and, when inhaled, can damage the lining of the lungs. Radon may also contribute to leukemia, although more studies are needed to verify a definitive link.

Living in a home with high radon levels increases the risk of developing lung cancer. The higher the gas concentration, the more likely those living in the house will develop cancer at some point in their lives. The risk of developing radon-related lung cancer also increases substantially if the home’s inhabitants are smokers. EPA estimates reveal the correlation between a home’s radon level and the risk of smokers who live there developing radon-related cancer. For example:

  • Of 1,000 smokers living in a house with a 1.3 pCi/L concentration of radon gas, approximately 20 could develop lung cancer.
  • As many as 62 of 1,000 smokers could develop lung cancer if they lived in a home with a 4 pCi/L radon gas level.
  • Approximately 150 smokers who live in a home with radon gas levels at 10 pCi/L could develop lung cancer. That rate is about 200 times the risk of dying in a house fire.

Is there such a thing as a safe level of radon?

While there are no safe radon levels, the EPA strongly recommends taking steps to reduce indoor radon levels if they occur in concentrations higher than 4 pCi/L. However, because radon isn’t safe at any level, they also suggest treating homes with radon levels between 2 and 4 pCi/L. According to the EPA, the average radon gas concentration in a home is about 1.3 pCi/L, which does not pose an appreciable risk to most residents living in the house.

Outdoor radon gas levels are typically just 0.4 pCi/L, a minuscule level that isn’t considered a health risk. Along with learning how to fix high radon levels, it’s helpful for homeowners to understand the consequences of living with high radon levels and selling or buying a house with high concentrations of the gas.

Will a radon disclosure protect me if I’m selling my home?

As a part of the home selling process, homeowners fill out a disclosure form that lists known material defects, such as foundation problems, termite infestation, and the condition of the HVAC system. However, what sellers must disclose varies from state to state, and not all states require sellers to reveal the presence of radon gas.

If your state doesn’t require radon gas disclosure (Zillow’s list of states’ disclosure requirements may come in handy), you still have the right to request a radon test before buying a house.

radon in homes


How do I get a radon test?

When making an offer on a house, buyers have the opportunity to have it tested for various issues, including the presence of radon. A mortgage lender will often require structural and mechanical inspections to ensure the loan is a wise financial investment, but a lender does not always require radon testing. You may specifically have to ask for a radon test, and payment is generally required upfront.

A professional radon test typically runs less than $200. According to the EPA, all houses should be tested for radon by a local mitigation contractor. For those who are curious about the radon gas levels in their homes, radon testing kits are also available for learning how to test for radon in your home. These tests typically cost less than $30, including the lab’s fee to process the results.

What does a radon test involve?

A radon professional is a technician equipped with a radon sniffer, a tool that detects the presence and concentration of radon in homes. Since radon is heavier than air, the technician may ask the homeowner to turn off the HVAC system an hour or two prior to testing, allowing any radon in the house to settle near the floor.

The technician will also leave charcoal-filled canisters in different areas of the house for several days; then the canisters will be retrieved and analyzed for the presence of radon. Though homeowner detection devices are useful, most real estate contracts will expect professional testing.

radon in homes


How does radon mitigation work?

If a radon test indicates high gas levels in a home, the EPA suggests having a professional radon mitigation contractor remedy the problem. Homeowners should first check with their State Radon Office to determine which certifications are necessary for radon mitigation work in their area.

Not all states regulate radon mitigation contractors or their services. In those states, the EPA recommends that the homeowner ask the contractor about their experience and whether they hold any type of related credentials, such as certification with the American Society for Testing and Materials (ASTM).

The purpose of radon gas removal is to reduce the level of the gas, not to eliminate it, since radon gas is not considered a significant risk in levels lower than 4 pCi/L. Radon reduction seeks to prevent radon from entering a house and remove existing radon from the home.

Preventing radon from entering involves sealing the areas where it can seep in, such as cracks in basement floors and walls, as well as gaps around service pipes. In some cases, it may also require installing a radon pipe under the basement to transfer radon gas away from the house. Removing existing radon involves the installation of ventilation fans to circulate radon-heavy basement air to the outdoors.

What happens if a test reveals that the home we want to buy has high radon levels?

Depending on the wording of the home buying contract, both buyer and seller may share the cost of mitigating the radon. If the contract doesn’t specify who pays for mitigation, you can certainly ask the sellers to split the cost—and they may be willing to do so to help the sale go through. Professional radon reduction runs $800 to $2,500, with an average cost of about $1,200.

radon in homes


Should I buy a house that tests positive for radon?

According to the EPA, “Radon is a health hazard with a simple solution.” Once radon reduction measures are in place, home buyers need not worry about the quality of the air in the home. If a house you’re interested in tests positive for high levels of radon, odds are, other houses in the area are likely to have high levels as well. Since removing radon is relatively simple, your family will be safe in a home that has a radon reduction system in place.

Are there future radon risks to consider?

Even if a professional radon test reveals that a home’s radon levels are relatively safe, its levels can change over time. If the house settles, for example, a tiny foundation crack could allow the gas to seep in. For this reason it’s a good idea to install one or more radon detectors, such as the Corentium Home Radon Detector, on the lower floors of your home. These detectors alert you by beeping if radon levels rise, at which point you can take steps to mitigate the problem.

What to Do if You Think You’ve Been Exposed to Radon

radon in homes


If you think you’ve been exposed to high levels of radon gas, it’s a good idea to talk to your doctor. While most people who are exposed to radon gas won’t develop lung cancer, the doctor can at least make a note of the exposure and take proactive measures.

  • If the doctor feels it’s necessary, lung cancer screening, such as a low-dose CT scan, can be used to determine the presence of lung cancer.
  • The risk of developing radon-related lung cancer reduces if radon levels in the home are lowered.
  • Smokers who have been exposed to radon can reduce their risk of developing lung cancer by stopping smoking.

Final Thoughts

Radon is a natural gas, and it’s found virtually everywhere. However, it is only considered dangerous in high concentrations. Fortunately, radon mitigation is a relatively straightforward process of diverting the gas away from a home’s foundation. Radon mitigation costs an average of $1,200, depending on the size of the house and local labor prices. The cost of radiation detection and control is still less than the typical medical bills related to lung cancer.

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