How to Test for Radon in Your Home

You can test for radon yourself with a $15 to $40 kit, or hire a professional for $125 to $350. Both methods work. The right choice depends on your timeline, budget, and whether the results need to satisfy a lender or buyer. Here is how to decide and how to do each one correctly.

Radon is a radioactive gas that seeps into homes through the soil. You cannot see it, smell it, or feel it. Testing is the only way to know your levels. The EPA estimates that 1 in 15 homes in the United States has radon at or above 4 pCi/L, the federal action level.

DIY Radon Testing

A home radon test is one of the simplest diagnostic tests you can run. You place a small device in your home, leave it undisturbed, and either read the result directly or mail it to a lab. There are three categories of DIY radon test kits.

Charcoal Canister Kits ($15 to $25)

Charcoal canisters are the most common and cheapest short-term radon test. The activated charcoal absorbs radon from the air over a 2 to 7 day period. After exposure, you seal the canister and mail it to a lab. Results arrive within one to two weeks.

Where to buy: hardware stores (Home Depot, Lowe's), Amazon, Walmart, or through your state radon program. Many states offer free or discounted test kits. Check your state health department website.

Charcoal kits are a good first screening tool. They give you a snapshot of radon levels during the test window. Keep in mind that radon levels fluctuate daily and seasonally, so a single short-term test is a starting point, not the final word.

Alpha-Track Detectors ($20 to $40)

Alpha-track detectors are the standard for long-term radon testing. You place the detector in your home for 90 days to one year, then mail it to a lab. The detector records alpha particle strikes on a small piece of plastic film, giving you a true seasonal average.

Long-term tests are more accurate than short-term tests because they smooth out daily and seasonal fluctuations. If you are not in a rush, an alpha-track detector is the best DIY option for understanding your actual year-round exposure.

Electronic Radon Monitors ($100 to $200)

Continuous electronic radon monitors, such as the Airthings Wave and Ecosense RadonEye, give you real-time radon readings on your phone or the device display. They are reusable, so the upfront cost pays for itself after a few uses.

These monitors update hourly or daily and let you see how radon levels change with weather, HVAC operation, and season. They are not certified for real estate transactions, but they are excellent for ongoing monitoring after mitigation or for tracking your levels over time.

How to Run a DIY Radon Test: Step by Step

Choose your test location. Place the test on the lowest livable level of your home. This is typically the basement if you use it as living space, or the first floor if you have a slab foundation. Do not place it in a closet, bathroom, kitchen, or laundry room. Avoid areas with high humidity, drafts, or direct sunlight.
Set up closed-house conditions. Close all windows and exterior doors at least 12 hours before starting the test and keep them closed for the entire test period. Normal entry and exit through doors is fine. Keep HVAC systems running normally, but do not operate fans that bring in outside air.
Place the device correctly. Set it at least 20 inches off the floor, at least 3 feet from exterior walls, and away from drafts, vents, and windows. A table or shelf in the middle of the room works well.
Do not disturb the device. Leave it in place for the entire test period. Do not move it, cover it, or place anything on top of it.
Seal and mail (for passive kits). When the test period ends, seal the canister or detector as directed and mail it to the lab the same day. Charcoal kits are time-sensitive; delays can affect accuracy.

Professional Radon Testing

Professional radon testing costs $125 to $350 depending on your location and the number of test points. A certified radon tester places one or more continuous radon monitors (CRMs) in your home for a minimum of 48 hours and retrieves them to generate a detailed report.

What Professionals Use: Continuous Radon Monitors

CRMs record radon levels every hour, producing a full timeline of readings throughout the test. This data reveals spikes, patterns, and whether the overall average is reliable. CRMs are calibrated annually and produce tamper-evident reports that document the chain of custody from placement to retrieval.

Unlike passive kits, CRMs can detect if someone opened windows or moved the device during the test. This tamper resistance is one reason lenders and real estate attorneys accept professional CRM results.

When Professional Testing Is Required

Real estate transactions. Most lenders and buyers require a professional radon test performed by a certified tester. DIY kits are generally not accepted during a home sale.
Post-mitigation verification. After a radon mitigation system is installed, a professional re-test confirms the system is working. Many mitigation companies include this in their installation price.
Legal disputes. If radon test results factor into a legal claim, such as a disclosure dispute, professionally documented results carry more weight.
Multi-family or commercial buildings. Testing protocols for apartments, schools, and workplaces often require certified professionals and CRM equipment.

Short-Term vs. Long-Term Radon Testing

	Short-Term Test	Long-Term Test
Duration	2 to 7 days	90 days to 1 year
Best for	Quick screening, real estate	Accurate seasonal average
Accuracy	Snapshot of one period	Reflects year-round conditions
DIY cost	$15 to $40	$20 to $50
Professional cost	$125 to $350	N/A (pros use short-term CRMs)
Accepted for real estate	Yes (pro CRM required by most lenders)	No (takes too long for transactions)

The EPA recommends starting with a short-term test. If the result is below 4 pCi/L, follow up with a long-term test to confirm. If the result is 4 pCi/L or above, either do a second short-term test to confirm or proceed directly to mitigation.

When to Test for Radon

Test your home for radon in any of these situations:

You are buying or selling a home. Radon testing is standard during the home inspection period. Buyers should insist on a professional test; sellers can test proactively to avoid surprises.
Your home has never been tested. Every home should be tested at least once, regardless of location, age, or construction type.
You completed major renovations. Changes to your foundation, HVAC system, or the addition of a new basement living space can alter radon entry and airflow patterns.
It has been more than 2 years since your last test. The EPA recommends re-testing every 2 years, even if previous results were low. Soil conditions, foundation settling, and changes to your home can shift radon levels over time.
You installed a mitigation system. Test within 24 hours to 30 days after installation, then re-test every 2 years to verify the system is still performing.

Common Radon Testing Mistakes

A radon test is only useful if it is done correctly. These mistakes can produce misleading results:

Testing in the wrong location. A test placed in an unused crawl space, a rarely entered attic, or an upper floor will not reflect the radon levels where you actually spend time. Test the lowest level of your home that you use regularly.
Opening windows during the test. Open windows dilute indoor radon and produce artificially low readings. Keep windows and exterior doors closed for the 12 hours before and throughout the entire test.
Moving the device. Picking up, bumping, or relocating the test kit during the testing period invalidates the results. Place it once and leave it.
Testing during unusual weather. Severe storms, sustained high winds, or unusually warm weather can temporarily alter radon levels. If conditions were extreme during your test, consider re-testing.
Placing the kit near drafts or vents. Air movement from HVAC vents, ceiling fans, or open windows directly affects the readings. Keep the device away from any air disturbance.
Delaying the mail-in. Charcoal kits continue to change after the test period ends. Mail them the same day you seal them. Delays of even a few days can skew results.

What to Do With Your Results

Radon test results are measured in picocuries per liter of air (pCi/L). Here is how to interpret your reading:

Below 2 pCi/L: No action needed. This is a low level, close to the average outdoor concentration of 0.4 pCi/L. Re-test every 2 years.
2 to 4 pCi/L: Consider a long-term follow-up test to get a more precise annual average. The EPA action level is 4 pCi/L, but the World Health Organization recommends action at 2.7 pCi/L. There is no known safe level of radon exposure, so reducing levels in this range is still beneficial.
Above 4 pCi/L: Mitigate. Install a radon mitigation system to reduce levels below 2 pCi/L. Most systems cost $800 to $2,500 and reduce radon by 80% to 99%.
Above 8 pCi/L: Mitigate promptly. At this level, the EPA compares your radiation exposure to smoking half a pack of cigarettes per day. Do not wait for a follow-up test; contact a certified radon mitigator.

After mitigation, run a post-installation test within 24 hours to 30 days to confirm the system is working. Then re-test every 2 years.

Find a Certified Radon Tester

Whether you want a professional test for a real estate transaction or need a post-mitigation verification, a certified tester follows EPA protocols and uses calibrated equipment. Find a certified radon tester near you through our directory of NRPP and NRSB-certified professionals.

Frequently Asked Questions

How much does radon testing cost?

A DIY radon test kit costs $15 to $40, depending on the type. Professional radon testing costs $125 to $350 and uses continuous radon monitors that record hourly readings. Professional tests are required for most real estate transactions.

Can I test for radon myself?

Yes. DIY radon test kits are available at hardware stores and online for $15 to $40. Place the kit on the lowest livable level of your home, maintain closed-house conditions, and mail it to a lab after the test period. Results arrive within one to two weeks.

How long does a radon test take?

A short-term radon test takes 2 to 7 days. A long-term test takes 90 days to one year and provides a more accurate seasonal average. Professional tests using continuous radon monitors require a minimum of 48 hours.

What is a safe radon level?

The EPA recommends taking action at 4 pCi/L or above. The World Health Organization sets a lower threshold at 2.7 pCi/L. There is no known completely safe level of radon exposure, but levels below 2 pCi/L are considered low risk.

When should I test my home for radon?

Test when buying or selling a home, if your home has never been tested, after major renovations, after installing a mitigation system, or if it has been more than 2 years since your last test. The EPA recommends re-testing every 2 years.