Radon Inspection and Testing Guide

Written by Angela Bunt Updated 03/19/2024

Our team highly encourages homeowners to perform a radon test, particularly if you’re building or buying a home. All homeowners should take this important safety measure, as radon exposure can have hazardous consequences. This guide explains the health risks of radon exposure, prevention measures, and how to inspect your home.

What Is Radon?

Radon (Rn) is an odorless, colorless, tasteless radioactive gas that naturally occurs in soil and water, particularly groundwater. While only a small percentage of radon originates from drinking water, according to the Environmental Protection Agency (EPA), radon exposure is the second leading cause of lung cancer after smoking. It significantly increases the risk of lung cancer in smokers especially.

The only way to know if there’s a harmful amount of radon in your home is to perform a radon test. For optimal results, the test must be performed according to the test manufacturer’s instructions.

It must be stressed that any home can have a harmful radon level, defined as a level of radon that’s hazardous to your physical health. The EPA recommends that all homeowners test their homes for radon; however, some homes are more likely to have harmful radon levels than others.

Your location determines how likely your home is to have a high radon level. The EPA website provides a map of radon zones by state and county. Level 1 or 2 is considered high.

Neighborhoods within a county can have a higher or lower radon level than is indicated on the map. Another factor is that soil under your home could have been obtained from an area with high levels of radon. These variables underscore why the EPA recommends testing all homes.

In the video below, This Old House Host Kevin O’Connor talks about radon testing, safe levels, and mitigation with home technology expert Ross Trethewey.

When To Test for Radon

Certain states require home buyers perform a radon test when they purchase their home. In fact, many home inspectors, especially those in high radon areas, provide radon tests as an added service.

Consider performing a radon test even if you did not do so when you bought your home, particularly if you live in a Level 1 or 2 area. You can test your home for radon yourself or hire a professional.

After your radon test, you don’t need to test again if your home has a non-harmful radon level and you don’t make significant changes to your property. If your home does show a harmful level of radon, there are several effective mitigation options. Perform another test right after your radon mitigation, and then every few years following. This ensures the radon reduction system is functioning properly.

Types of Radon Tests

In general, are two types of radon tests:

Passive devices for radon detection include alpha track detectors, charcoal canisters, and charcoal liquid scintillation detectors. After using one of these methods, the passive device is returned to a laboratory for analysis.

You can purchase charcoal canisters for short-term use through the National Radon Program Services website. These and other DIY tests are easy to use and affordable, costing $10–$50. However, they’re less precise and can produce inaccurate results due to improper test conditions or the weather.

Requiring power to function, active devices include different types of continuous monitors and continuous working level monitors. Active devices should be operated by trained testers, and these tests often cost more than passive testing.

Active devices are usually intended to be used for three months to a year before being returned to the providing laboratory for analysis. They’re more precise and read out variations in radon levels throughout the test period.

How To Perform a Radon Test

Closely follow the test manufacturer’s instructions when performing a radon test. Failure to do so can produce an inaccurate result. A incorrect “fail” result can lead you to install an unnecessary radon mitigation system, and a false “pass” result can expose you and your loved ones to dangerous radon levels.

Here are some best practices for radon inspection tests:

Keep windows and doors closed, except for usual entry and exit from the home.
Place the test device on the home’s lowest occupiable level, either the basement or first story.
Keep the test device away from your heating and cooling supply as well as vents, exhaust fans, ceiling fans, whole-house fans, clothes dryers, and any other sources of air movement or high humidity.
Test in an area that is not a bathroom, laundry room, kitchen, or closet.
Place the test device 2–3 feet above the floor, 1–3 feet away from exterior walls, 4 inches from any object, and in a location where it won’t be disturbed.
Use the heating and cooling system in a normal manner. Turn off all moving air devices such as ceiling fans, dehumidifiers, regular fans, high efficiency particulate air (HEPA) or any other kind of filtering devices.
Avoid performing the test during storms or high-wind events.

Radon Test Limitations

Radon tests are not always 100% accurate. These factors can cause inaccurate results:

Device malfunction

Failure to follow test manufacturer’s instructions

Leaks in heating and cooling ducts, especially in crawl spaces, return ducts, and unconditioned basements

Short test periods that don’t account for weather and seasonal factors

Time of year (radon levels can be lower during summer)

Unusual weather conditions, especially high wind and high humidity

What Are Actionable Levels of Radon?

An actionable level of radon means there’s a high concentration in your home and the problem needs to be addressed promptly. Radon is measured by picocuries per liter (pCi/L). A level between 0 and 2 pCi/L is considered non-actionable—there’s no need to worry. A level between 2 and 4 pCi/L is considered marginally actionable. A level above 4 pCi/L is considered actionable, and you should seek professional help.

Dealing With Radon Issues

Discuss radon mitigation measures with your contractor before constructing a new home, particularly if you’re building in a Level 1 or 2 radon zone, the most susceptible zones. The most common mitigation methods are installing a quality vapor retarder or sub-slab ventilation under concrete floors.

A vapor retarder, sometimes called a vapor barrier, uses a vapor barrier, fans, and piping to create a low-pressure environment that gathers radon underneath the home. Sub-slab ventilation works similarly, involving a stone layer with one or more pipes under the concrete. A fan is connected to the pipes, creating suction that routes radon from the home safely outside.

Similar mitigation measures can be installed in existing homes, especially those built on a crawl space or unfinished basement. However, installing vent pipes under an existing concrete floor could be less effective because the pipes may only capture nearby gas.

A qualified radon mitigation contractor should perform these intricate measures.

DIY radon mitigation can sometimes be effective for relatively low radon levels.

Here are some typical DIY mitigation measures:

Seal cracks in concrete floors as well as the joint between the floor and wall. Use a high-quality sealant and apply it according to the manufacturer’s instructions.
Seal leaks in heating and air conditioning ducts as well as equipment located in crawl spaces and basements. Use mastic or foil tape intended for this purpose.
Seal openings between occupied areas of your crawl space and basement. This includes openings for plumbing pipes, plumbing fixtures such as bathtubs, electrical wires, and heating and air conditioning ducts and pipes.

Our Conclusion

Radon testing and mitigation can be complicated, but it’s essential to protect you and your loved ones. We recommend hiring a qualified radon testing and mitigation professional if you aren’t comfortable with DIY projects or would rather just leave it to the pros.

Radon Resources

The following resources provide additional information on radon testing and mitigating radon risks:

FAQ

Is radon testing really necessary?

Yes, radon testing is necessary for all homeowners, as radon exposure can have hazardous consequences. The EPA recommends that all homeowners test their homes for radon.

What houses are most at risk for radon?

While any home could be at risk of having high levels of radon, some homes are more likely to have harmful radon levels than others. The EPA website provides a map of radon zones—homes located in a Level 1 or 2 area are considered high risk.

Should I walk away from a house with radon?

While it’s important to know whether or not a home has unsafe levels of radon, high radon levels don’t mean that you need to walk away from purchasing a particular home. There are several options to successfully deal with radon and make a home safe for all inhabitants.

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