Best radon test kits and monitors

A short test does one job well, which is ruling out a low home. A 2024 review of 20 studies found that a one-week test predicted the annual average with over 95% confidence below about 2 pCi/L, but succeeded only about half the time at moderate levels.² So trust a clearly low result, and plan on a second test for anything near 4. This kit runs 2 to 4 days, which is shorter than that one-week test. Give it the full four if you can, because most studies in that review recommended at least four days for screening.^{2 3}

Timing is the weak spot. Kits ship twice a week and typically arrive 1 to 2 weeks after shipment, so this won't suit a home inspection window. Once the test ends, the kit must reach Alpha Energy Laboratories in Texas within 10 days, so mail it the same day. The program warns of severe delays in First Class mail and strongly encourages another shipping method, which you can buy when you register the kit online. New Jersey residents pay an added state fee and must register online, or the lab won't release results.³

An unopened kit doesn't expire as long as it stays in its plastic and the paper backing isn't punctured, so you can keep a spare for a fast second test.³

Radon moves from day to day and season to season, so a longer test tells you more. EPA says a test of more than 90 days is more likely to reflect your year-round average.⁴ One Ask This Old House segment shows the swing: a house with a low 3-day result later peaked at about 19 pCi/L on a monitor. That's one house and a peak rather than an average, but it's a fair warning about snapshots.¹⁰

Results near 4 are where this kit earns its place. If two short tests average 4.1 pCi/L, EPA says there's about a 50% chance that your year-round average is somewhat below 4.⁴ The error runs the other way too. In 158 Iowa homes, a winter basement test of 7 to 10 days missed about 12% of basements whose annual average was at or above 4.¹¹

The kit runs 3 to 12 months, and Radonova in Illinois does the analysis, not the lab that reads the short-term kit. It expires 5 years from manufacture.³ One long-term detector type did well in a 13-week underground test, where alpha-track detectors stayed within 6.5%.⁵ The program doesn't say which detector this kit uses, so that result may not carry over.³

No monitor in this guide has more independent support. C-NRPP, Canada's radon certification program, runs 7-day chamber rounds at about 6, 12 and 30 pCi/L, and gives an A for measurement error of 10% or less. This monitor earned an A in all four rounds in 2023 and again in 2024/25.^{7 8} In a study of 15 monitors led by Health Canada scientists, the RD200 fell in the group that came within 22% of reference instruments. That group mostly read slightly high, at up to about 1.23 times the reference, and the RD200 read slightly low, at about 0.95 to 0.98, in one round at a much higher radon level.⁵

It also reacts quickly. In a Spanish field comparison, RadonEye models lagged the reference by 1 to 3 hours, while three Airthings models lagged by 5 to 15 hours.¹² That helps when you're checking whether a mitigation system works. The advertised 10-minute first reading is another matter. It isn't a test result, and short readings can mislead in either direction.^{13 14 15}

Two homeowner videos are positive. One owner ran it beside other monitors and saw 1.97 pCi/L against about 2 to 2.3 on the others, though none of them was a calibrated reference.¹⁶ Another used its trend graph to spot levels near 6 pCi/L while his house was shut up.¹⁷

It plugs in, and C-NRPP lists its long-term averages on the app, not the display, so you depend on a phone and Bluetooth.^{13 14} Ecosense's warranty runs one year, or two if you register within 30 days.¹⁴

This is the simplest monitor to live with. Airthings says it runs up to 3 years on two AA batteries, and the screen shows 24-hour, 7-day, 30-day and long-term averages, so you can read it without a phone. Bluetooth is there if you want the Airthings app. The free 5-year warranty needs registering within 30 days.⁹

The trouble is that the test record belongs to the older Corentium Home. That model fell in Health Canada's passing group and earned four As from C-NRPP in 2024/25, after B, A, B, A in 2023 (a B means error above 10% and up to 20%).^{5 7 8} The Home 2 isn't in any of those tests, so its accuracy rests on Airthings' own claim of within 10%.⁹

Low readings are the bigger worry. In a 13-week test at about 3 pCi/L in an underground lab, Airthings devices missed by more than 20%, and the same paper cites an earlier study that put the Corentium Home 48 to 61% off below about 5 pCi/L.⁵ An underground lab isn't a house, but don't treat a reading of 3 on this monitor as proof that you're safely below 4. A long-term lab kit is a useful cross-check.⁵

Owner evidence is thin. One video likes the app and battery life, but it covers only a few days of use with no reference device.¹⁸ A homeowner who ran an older Airthings beside other monitors said he'd pick it if buying just one, while noting that it updates slowly.¹⁶