What Is Radon? Guide to Radon Testing and Abatement


If you’re planning to buy or sell a home, you need to know about radon testing. Radon has been in and out of the news over the past 30 years, described alternately as a major danger and overblown hype. 

So what’s a homeowner to do?

Knowledge is power. Here’s everything you need to know about radon.

What Is Radon?

Radon is a colorless, odorless, tasteless gas that occurs naturally. It is formed when uranium breaks down over time. When uranium decays, it releases radon gas as a byproduct. Radon gas is also radioactive, so it can be dangerous to humans.

Most people think of uranium as a rare, valuable mineral. In reality, uranium is found in small amounts in many types of rocks. As these rocks break down over time, uranium is released into soil and groundwater. As that uranium further decays, radon is released.

On an atomic level, radon gas has only one atom per molecule. This means that radon particles can easily move through the spaces between atoms in solid surfaces. Radon can penetrate concrete and common building materials like wood and sheetrock.

Because radon can move through solid materials, it can easily permeate the foundation of your home. Over time, radon gas can build up and lead to problems. 

The Problem With Radon

Radon is radioactive. Radioactive substances are carcinogens that can cause cancer. In particular, scientists have found that radon causes between 15,000 and 22,000 lung cancer deaths each year in the United States. Smokers are more likely to have lung cancer, but 10% of radon-related cancers occur in non-smokers.

Tiny amounts of radon gas are all around us, and we breathe it every day. In natural quantities, radon isn’t a problem. When radon builds up in your home, it can be very dangerous. Here’s what happens:

  1. Rocks and soil break down naturally.
  2. Radon gas is released.
  3. As the gas rises, some seeps through your home’s foundation.
  4. Radon gas is trapped in your basement or another part of your home such as crawlspace or in slabs, where it builds to dangerous levels instead of dissipating into the atmosphere.
  5. Gas eventually permeates into the rest of the home.
  6. Humans breathe in radon, and over time it can cause lung cancer.

Pro-Tip: A common misconception is that radon is only an issue in homes with basements. This is not true, and elevated levels of radon are routinely found in homes without basement, for example in homes with slabs and also in crawlspaces.

When to Test for Radon

According to the Environmental Protection Agency (EPA), all homeowners should test their homes for radon. Radon has been found in all 50 states and in all types of houses, so it’s impossible to predict which homes are safe without a radon test.

The EPA recommends that you test your home when you prepare to sell. If you’re buying a house, you should insist on radon testing as part of the home inspection before you commit to the sale. If the results show high levels of radon, negotiate the sales price to cover radon abatement before you buy.

Radon can be found anywhere. Here are only a few examples of risk factors to consider:

  • Location: Some regions are known to have higher radon rates than others. The Appalachian Mountains and Upper Midwest have higher rates, while the Southeast has lower rates. Check the EPA’s map to estimate your risk. This map does not guarantee that your house is risk-free from potentially elevated radon levels.
  • Foundation Type: Older homes with dirt floors in the basement since there is nothing to slow the rise of radon gas from the soil. Exposed crawl spaces also allow radon to rise into living areas unchecked. 
  • Foundation Damage: Radon can seep through concrete, but foundation slabs and walls with cracks are prime areas where extra gas can seep in.
  • Other Construction Gaps: Any gap in the foundation can allow radon to enter the home. Common examples are gaps around pipes and wires, construction joints where walls and floors meet, and open sump pumps.
  • Well Water: Radon can also be found in groundwater. If you rely on a well, it’s a good idea to test your water regularly for contaminants, including radon.

How to Test for Radon in Your Home

To get the most accurate results, it’s best to work with a home inspector for your radon testing. A qualified inspector knows exactly where to place the radon test to get the best read-out, and he or she will also be able to inspect the rest of your home for problem spots where radon can seep in.

1. Short-Term Radon Tests (Cheap But...)

When you want a quick snapshot of your radon levels, a short-term test maybe a way to go. These are available at hardware stores and home improvement centers. Short-term tests are usually made of activated charcoal that captures radon over the course of three days to a week. When the test is complete, you can mail it to a lab for analysis.

While relatively quick and easy, there are several drawbacks with short-term tests. The tests are generally not good at eliminating the interference that can lead to false results or measurement noise. The results are not based on continuous monitoring, see below for more information on continuous monitoring.

2. Continuous Radon Tests

The Continuous Radon Tests are conducted through devices that measure the concentration of radon over a period of time, typically 48 hours. The typically conducted by professional inspectors, who place the device(s) in the home strategically, based on the home configuration. The device will then monitor the radon levels over 48 hours while reducing or eliminating any interference or false results or “measurement noise.” The inspector collects the device after 48 hours, and subsequently provides a report based on the measurements taken by an expensive and relatively sophisticated device.

3. Long-Term Radon Tests

Long-term tests tend to more accurate than short-term ones described in #1 above because they use alpha particle tracking to determine radon levels. These tests can collect radon gas for a period of three months to a year. Factors such as wind gusts, snow pack and soil moisture will even out over the test period. The drawback with this approach is that it requires the homeowner to have a device plugged in for a long period of time. If there's a risk factor in the house, you would want to find out about it sooner.

The Verdict: A Continuous Radon Test conducted by a professional inspector is optimal for reliability (devices used are expensive and sophisticated) and accuracy (aided by a pro such as an inspector and a third party lab that knows how to interpret the results produced by a sophisticated device) in a relatively short period of 48 hours. The long-term tests are good in terms of accuracy but require a larger measurement period, and you may be exposed to elevated levels for that time if radon is indeed an issue in your house. 

Understanding Your Radon Test Results

Radon is measured in picoCuries per liter (pCi/L). Though no level of radon is considered safe, the EPA has set guidelines for acceptable levels. If your test results show radon levels at 4 pCi/L or higher, you should definitely take radon abatement measures to reduce the amount of gas in your home and lower your risk for radon-related lung cancer. If your radon levels are between 2 and 4 pCi/L, you can consider taking steps to lower the levels. 

What to Expect From a Radon Abatement

If your radon testing shows that you have elevated radon levels, you’ll need to hire a qualified professional for radon abatement. This will require the installation of a radon mitigation system that uses a fan to draw radon gases through a pipe from your foundation to the outdoors. Installation can typically be performed in one day and requires workers to cut a hole in your basement floor so the pipe can touch the earth. The pipe leads to a fan, which runs continuously to draw radon through the pipe. A hole will also be cut into the wall of your home so the pipe can release gas into the atmosphere outside your home, where it is harmless.

Radon abatement may also include filling in any cracks in the foundation and sealing gaps around pipes, sump pumps and other points of entry — including those made by installing the radon abatement system.

The Bottom Line

Cancer-causing radon is a serious issue in many homes, but it can be easily resolved. It’s always best to know what you’re getting into when buying a house, so be sure to hire a knowledgeable home inspection company before you buy.

Experts from WIN Home Inspection can easily add radon testing to your residential home inspection to mitigate surprises when you move into your new home. Click here to find a WIN Home Inspection expert near you. Alternatively, call (800) 309-6753 or email us at inquiry@wini.com and one of our experts will contact you promptly.