Best Radon Test Kits and Monitors for Homeowners (2026)

Radon is a radioactive gas that seeps up from the soil into houses, and you cannot see, smell, or taste it. The EPA estimates it causes about 21,000 lung cancer deaths in the U.S. each year, making it the second leading cause of lung cancer overall and the leading cause among non-smokers; about 2,900 of those deaths are people who never smoked. Nearly 1 in 15 U.S. homes is estimated to have an elevated level, and the EPA and the Surgeon General recommend testing every home below the third floor.

If you just bought a house, the seller's test may be old, taken on a floor you don't use, or missing. This guide covers lab kits vs. digital monitors, how to test so the result counts, what the number means, and what to do if it's high, then compares two lab kits and two monitors. January is National Radon Action Month, but if you just got the keys, put a test on your first-30-days list now.

What Radon Is and What the Number Means

Radon comes from the natural breakdown of uranium in soil, rock, and water. It rises through the ground, gets in through cracks, joints, and gaps around pipes, and the house traps it. The EPA says any home can have a problem, new or old, drafty or sealed, with or without a basement, and a neighbor's result is not a good guide to yours.

Radon is measured in picocuries per liter of air (pCi/L). The EPA's numbers:

• 4 pCi/L or higher: fix the home. This is the EPA's action level.
• 2 to 4 pCi/L: consider fixing. The EPA says no level of radon is safe, and most homes can be brought to 2 pCi/L or below.
• About 1.3 pCi/L: the estimated average indoor level. Outdoor air averages about 0.4 pCi/L.

For scale, the EPA estimates that of 1,000 people who never smoked living at 4 pCi/L over a lifetime, about 7 could get lung cancer; of 1,000 smokers, about 62. Smoking plus radon is an especially serious combination.

Lab Kit or Digital Monitor?

Short-term lab kits

A short-term test stays in the house for 2 to 90 days, depending on the device. The usual homeowner version is a charcoal kit you leave out a few days and mail to a lab. Because radon varies day to day and season to season, the EPA says a short-term test is less likely to reflect your year-round average, but it is the fastest way to find out whether you have a problem.

Long-term lab kits

A long-term test stays in place more than 90 days, usually as an alpha-track or electret detector, and gives the reading most likely to match your year-round average, which is what the action level is really about. The trade-off is waiting three months or more.

Consumer digital monitors

A digital monitor shows a running radon average on a screen or in an app, for years, which makes it good for seeing seasonal swings and keeping watch between lab tests. The limit is proven accuracy. The Conference of Radiation Control Program Directors, representing state radiation programs, says consumer monitors' accuracy and reliability have not been verified by an independent third party, and that they are not for real estate transactions or mitigation decisions. Wisconsin's radon program recommends confirming a high monitor reading with an approved short-term charcoal kit or a long-term kit. Get the number you act on from a lab kit, and add a monitor to watch it over time.

How to Test So the Result Counts

These rules come from the EPA's A Citizen's Guide to Radon and Home Buyer's and Seller's Guide to Radon. Follow your kit's instructions too.

• Lowest lived-in level. The basement if you use it regularly, otherwise the first floor. If you might use the basement as a family room, play area, or workshop, test there.
• A room people use. A living room, den, playroom, or bedroom. Not a kitchen, bathroom, laundry room, furnace room, closet, stairway, hallway, or crawl space.
• Placement. At least 20 inches above the floor, undisturbed, away from drafts, high heat, high humidity, and exterior walls.
• Closed-house conditions. For a short-term test, keep windows and outside doors closed except for normal coming and going, starting at least 12 hours before a test of two to four days. Heating and cooling that recirculate indoor air can run; fans that bring in outside air cannot.
• Weather. Don't run a test of four days or less during severe storms or high winds.
• Time and mail. Any radon test should run at least 48 hours. Leave the kit out as long as the package says, note the start and stop times, reseal it, and send it to the lab right away.

What to do with the result

1. Take a short-term test. Below 4 pCi/L, you can stop for now; test again in the future, and retest on the lower level if you start living in the basement.
2. At 4 pCi/L or higher, test again to be sure. A long-term test gives a better picture of your year-round average; a second short-term test is faster. If the first result is more than twice the action level, take the second short-term test immediately.
3. Decide. Fix the home if the long-term result is 4 pCi/L or more. With two short-term tests, the EPA says to consider fixing if their average is 4 or higher; the higher the results, the more certain you can be.

Results near 4 are the hardest to call: if two short-term tests average 4.1 pCi/L, the EPA says there is about a 50% chance your year-round average is somewhat below 4.

If the Number Is High

Radon problems are fixable. The EPA says most homes can be fixed for about the same cost as other common home repairs, and some systems cut radon by up to 99%. The standard fix is sub-slab depressurization, or soil suction: a pipe goes through the basement floor or slab into the gravel or soil beneath, and a fan pulls radon from under the house and vents it outdoors. Similar systems work in crawl spaces.

Sealing is part of the job, not the whole job. Sealing foundation cracks and openings makes a suction system work better, but the EPA does not recommend sealing alone, because by itself it hasn't been shown to lower radon significantly or consistently. The sump pit follows the same logic: the EPA describes sump-hole suction, where the sump is capped so it keeps draining water while serving as the suction point. A sealed lid is part of a radon system, not a substitute for one; our sump pump guide covers the pump side.

Hire a qualified contractor

Lowering radon takes technical knowledge and special skills, the EPA says, so use a trained radon contractor. Your state radon program can point you to one; states that receive EPA radon grants list only providers credentialed by the state or by one of the two national programs, the National Radon Proficiency Program (NRPP) and the National Radon Safety Board (NRSB). Get more than one estimate, and since the EPA flags a conflict of interest when one firm both tests and mitigates, keep your own testing independent. This is a hire-a-pro job (see DIY vs. hire a pro); if you want to try it yourself, the EPA says to call your state radon office first. A contractor may also recommend having a qualified inspector check your fuel-burning appliances for backdrafting; if so, get it done, and make sure your CO alarms are current.

Test again after the fix

The EPA says to test within 30 days of installation, but no sooner than 24 hours after the system starts running, for two to seven days, with windows and doors closed, except for normal coming and going, from 12 hours before the test until it ends, done by an independent tester or by you, not only by the contractor. The fan must run continuously; most systems include a monitor showing whether it's working. Retest at least every two years and after any major renovation.

At a Glance

Picks Worth Buying

1. Best first test — the lab kit to start with

The RD1 uses activated charcoal and sits two to four days in the lowest level of the house before going straight into the mail. First Alert says the lab fee is included (New Jersey residents must send an extra state-required fee) and results are available three to five business days after the lab receives the kit. The manual says Alpha Energy Labs, which it describes as NRPP-certified, does the analysis. An unopened kit doesn't expire while its bag stays sealed, so buy two for a possible follow-up. Pros: the quickest route to a lab-reported number, lab fee included, simple instructions. Cons: a two-to-four-day snapshot of a level that shifts with weather and season; it only works if you mail it promptly; a high result means running another test. Best for: the first test in a new house, and the follow-up when the first one comes back high.

2. Best long-term test — your year-round average

A long-term test is the closest thing to a straight answer on whether your house averages above 4 pCi/L. AccuStar's detector starts measuring when you open its sealed bag and sits undisturbed for 91 to 365 days; the maker can't report a result under 30 days. Lab analysis is included, and AccuStar's lab lists NRPP and NRSB certifications. Its placement advice is close to the EPA's: the lowest level used regularly, not a kitchen, laundry, bathroom, crawl space, furnace room, or closet, at least two feet off the floor and three feet from exterior doors and windows. Pros: the result closest to your annual average; no power, nothing to set up; no strict closed-house rules like a two-to-four-day test, though Wisconsin's radon program suggests timing it so the house is closed up for at least half the test and it covers both heating and non-heating seasons. Cons: at least three months before you have a number, with nothing to read along the way; easy to forget, so put the mail-by date on your maintenance calendar. Best for: confirming a borderline short-term result when you aren't in a hurry, and learning your real level in a house you plan to stay in.

3. Best digital monitor — battery-powered, no app required

Pull the battery tab and the Corentium Home 2 starts measuring; two AA batteries last up to three years (up to two if you keep it connected to the app by Bluetooth), so it works in a basement or bedroom with no outlet nearby. The first 24-hour average appears after one full day, and after 30 days the screen cycles through all four averages plus temperature and humidity. It works without the app; the free Airthings app over Bluetooth adds graphs, and remote alerts need an Airthings hub or View monitor. Airthings rates it at 0 to 250 pCi/L, with accuracy and precision within 10% after 4 days at 10 pCi/L or 7 days at 5.4 pCi/L. Pros: no wiring or Wi-Fi needed, readable at a glance, long battery life. Cons: nothing to read for the first day and the full set of averages only after 30 days; Bluetooth only unless you add an Airthings hub; like every consumer monitor, state programs say it isn't for real estate or mitigation decisions. Best for: tracking your level through the seasons, and keeping an eye on a mitigation system between lab tests.

4. Best real-time monitor — fast readings and an alarm

The RadonEye is for people who want to see radon move: it plugs into an outlet, uses a pulsed ionization chamber sensor, and shows its first reading on an OLED screen after 10 minutes, updating every 10 minutes after that. The Bluetooth app records an hourly average, and the Bluetooth app shows that history as trend charts. Ecosense rates it for up to 1,000 square feet and says it is approved by C-NRPP, Canada's radon proficiency program; that is not a U.S. approval, and U.S. state programs treat it like any consumer monitor. Place it at least 20 inches above the floor and from the wall, away from open windows and vents, and at least 24 inches from Wi-Fi routers. Pros: the fastest feedback here, an audible alarm, detailed history in the app. Cons: needs an outlet, and a power outage resets the on-screen averages; the device has no clock, so weekly and monthly history lives only in the app; short readings swing a lot, so decisions still come from a lab test; a one-year warranty, two if you register within 30 days. Best for: data-minded owners, a basement you plan to finish, and seeing how the level responds to changes in the house.

How We Chose

We compare the category first — what a first-time homeowner actually needs from a radon test kit or monitor — then weigh manufacturer specifications, verified buyer feedback, and how the product type is used in real homes. We don't accept free products or payment for placement, and every pick names its compromise. How we research and review.

Frequently Asked Questions

Is the seller's radon test good enough?

Maybe. The EPA says to find out the result, who ran the test, where in the house it was taken, and what has changed since, such as renovations or heating and cooling work. If it is old, was taken on a higher floor than you plan to use, or didn't follow the EPA's testing checklist, retest. A short-term kit settles it once you move in.

Can I use a digital radon monitor instead of a test kit?

For watching trends, yes. For decisions, state programs say no: consumer monitors are not for real estate transactions or for deciding whether to mitigate, because their accuracy hasn't been independently verified. If a monitor reads high, confirm it with an approved short-term charcoal kit or a long-term kit, or hire a certified tester.

When is the best time to test for radon?

Whenever you can keep the house closed up for a short-term test, and soon after you move in. January is National Radon Action Month, and First Alert's instructions call winter the best time to test in northern climates. Test again after major renovations, before and after finishing a basement, and at least every two years if you have a mitigation system.

The Bottom Line

Start with a First Alert RD1 in the lowest room you use, set up the EPA way. Under 4 pCi/L, retest down the road. At 4 or higher, test again: a second RD1 for a quick answer, or an AccuStar Alpha Track for three months or more if the first result was close to 4 and you can wait. If the first result was above 8 pCi/L, twice the action level, the EPA says to run the second short-term test right away. Call a certified mitigation contractor if the follow-up confirms 4 or higher. To keep watching the number, add an Airthings Corentium Home 2, or an Ecosense RadonEye RD200 for real-time readings, and confirm anything high with a lab kit. Retest every two years once you have a system.

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