How to Test for Radon at Home

You can test your home for radon with an inexpensive do-it-yourself kit or by hiring a certified radon measurement professional. Place the test correctly, follow closed-house instructions, and use the result to decide whether you need a second test or a radon mitigation system.

Why Radon Testing Matters

Radon is a radioactive gas produced naturally as uranium breaks down in soil and rock. It has no color, smell, or taste, so testing is the only practical way to know whether it is building up inside a home.

Any home can have elevated radon, including new homes, older homes, homes without basements, and neighboring houses with very different results. Past test results also may not reflect current conditions after renovations, foundation work, HVAC changes, or long periods of time.

Choose the Right Type of Radon Test

Homeowners generally have three options:

• Short-term DIY test: Usually remains in place for two to seven days. Basic kits typically cost about $10 to $30, although laboratory fees may be separate.
• Long-term DIY test: Measures radon for 90 days to one year. These tests often cost about $20 to $50 and provide a better picture of the home’s average exposure.
• Digital radon monitor: A reusable electronic device that displays readings over time. Consumer models typically cost about $100 to $300.
• Professional test: A certified professional may charge roughly $100 to $250 for a standard home. Larger homes, multiple foundations, or additional test locations can increase the price.

Short-term tests are useful when you need an answer quickly, such as during a real estate transaction. Long-term tests are better for understanding normal seasonal variation. Professional testing is often the best choice when deadlines, documentation, or an independent result matter.

How to Test for Radon at Home Step by Step

1. Select the testing area

Test the lowest level of the home that is regularly occupied or could be used as living space. That may be a finished basement, a first-floor bedroom, or an unfinished basement that could reasonably be converted later.

For a large home or a house with separate foundation areas—such as a basement, slab, and crawl space—more than one device may be appropriate.

2. Prepare the home

For a short-term test lasting fewer than four days, begin closed-house conditions at least 12 hours before starting. Keep exterior doors and windows closed except for normal entry and exit.

You may operate heating and cooling systems that recirculate indoor air. Avoid running whole-house fans, window fans, or other equipment that brings in outdoor air. Do not conduct a short-term test during unusually severe storms or prolonged high winds if you can reasonably wait, because extreme conditions can affect the reading.

3. Position the device correctly

Follow the manufacturer’s instructions exactly. In general, place the test:

• At least 20 inches above the floor
• Where it will not be disturbed
• Away from exterior walls, windows, doors, and drafts
• Away from fireplaces, furnaces, and direct heat
• Out of direct sunlight
• Outside kitchens, bathrooms, laundry rooms, and other humid areas

A bedroom, family room, office, or basement recreation area is usually a suitable location. Do not place the device inside a cabinet, on the floor, or next to a sump opening.

4. Run the test for the required time

Record the start date and time. Leave the device untouched for the full testing period and maintain the required closed-house conditions.

Short-term tests commonly run for 48 hours to seven days. Long-term devices remain in place for at least 90 days. Opening windows, moving the device, or ending early can make the result unreliable.

5. Finish and submit the test promptly

For a mail-in kit, seal the device as directed and send it to the laboratory immediately. Delays can interfere with analysis, particularly with certain short-term devices.

Complete all requested information, including the test location, start and stop times, and whether closed-house conditions were maintained. Digital monitors may display results directly, but you should still review the manufacturer’s guidance for calculating or interpreting an average.

What Your Radon Result Means

Radon is measured in picocuries per liter of air, written as pCi/L.

The Environmental Protection Agency recommends taking action when the result is 4 pCi/L or higher. Because no radon level is considered completely risk-free, homeowners may also consider reducing levels between 2 and 4 pCi/L.

A single short-term result is a snapshot, not necessarily the home’s year-round average. If the first result is 4 pCi/L or higher, follow up with another short-term test or a long-term test. When the initial reading is substantially elevated, arrange the follow-up promptly and consider consulting a certified professional.

Testing During a Home Sale

Real estate timelines often make long-term testing impractical. A certified professional commonly uses a continuous radon monitor for at least 48 hours and produces a report showing hourly readings, test conditions, and possible device movement or interference.

Watch for these red flags:

• A device placed near an open window or exterior door
• Missing start and stop times
• No record of closed-house conditions
• A test moved during the measurement period
• Testing in an unsuitable room
• A seller-controlled test with no independent documentation

Buyers should review any existing radon report, but an old result should not automatically replace a current test. Ask when the test occurred, where the device was placed, and whether the home has changed since then.

What to Do If the Level Is High

Do not panic or assume the house is unsafe to purchase. Radon problems can usually be reduced with a properly designed mitigation system.

A common system uses a pipe and fan to pull radon-containing air from beneath the foundation and exhaust it above the roofline. Installation typically costs about $1,000 to $2,500, though complex foundations, finished spaces, crawl spaces, and local labor rates can raise the price.

Choose a certified mitigator who inspects the home, explains the proposed system, provides a written warranty, and includes or specifies post-installation testing. Be cautious of contractors who promise an exact final reading without inspecting the property, vent near windows, or say follow-up testing is unnecessary.

Find a certified radon professional near you

Frequently Asked Questions

How often should I test my home for radon?

Retest about every two years and after major renovations, foundation changes, HVAC modifications, or installation of a mitigation system. You may also test after moving into a previously untested lower level.

What is the best time of year to test?

You can test at any time. Short-term testing is often easier during heating or cooling seasons when windows are normally closed, while a long-term test provides a better annual average.

Can I test for radon myself?

Yes. A properly placed DIY kit can provide a useful result if you follow every instruction. Hire a certified professional when you need independent documentation or have unusual foundation conditions.

Should I test a home that already has mitigation?

Yes. Test after installation to confirm that the system works, then retest periodically. Check that the fan is operating and that any system monitor indicates normal performance.