Radon detectors

A radon detector, as the words are used in stores, is a small electronic device that measures radon on its own, over and over, and shows you the result. The current Canadian term is electronic radon monitor (ERM), which replaced the older "digital detector". It measures radon at regular intervals without a break and shows the result on its own screen, in a phone app or on a web dashboard. Some also store readings and measure temperature, humidity and pressure.

That makes a detector the opposite of a test kit in one useful way: a kit gives you one lab-read average for a fixed period, while a detector gives you a running record you can watch for months. It also brings two risks a kit does not have. A cheap detector may simply not measure radon well, and a detector's short-term readings are easy to over-read. This hub covers every monitor we have verified, with its independent evidence status beside it, how to choose, and how to use one so its average means something. For mailed kits, see radon test kits.

Electronic radon monitor (ERM)

The current Canadian term for an active radon device that continuously measures radon levels and provides near real-time readings. C-NRPP sorts ERMs into consumer-grade and professional-grade; the professional ones were previously called continuous radon monitors (CRMs).

The list at the top of this page holds every consumer radon monitor we have verified against its maker's own page. Beside each one is its independent evidence status: whether C-NRPP approved it in its 2024/25 evaluation or did not include it. The field studies that name some of these models are summarized further down. "Not included" means C-NRPP has published no result for that model, usually because its maker did not enter it; it is not a failed test. Maker's claims, such as accuracy figures, are attributed to the maker.

The principle fits in two sentences. Air reaches a detection chamber through a small pump or by natural diffusion. Inside, an alpha scintillator, an ionization chamber or a solid-state detector registers the alpha particles from radon and its decay products. On-board electronics then turn those counts into a radon level and report it for set time intervals.

1. 1Step 1 of 4:

   Air reaches the chamber

   Room air, and the radon in it, gets into the detection chamber by natural diffusion or through a small pump.

2. 2Step 2 of 4:

   Alpha particles are counted

   Radon and its decay products give off alpha particles. The detector in the chamber registers them.

3. 3Step 3 of 4:

   Counts become a concentration

   The on-board electronics turn what the detector registers into a radon level, in pCi/L or Bq/m3.

4. 4Step 4 of 4:

   Readings are averaged

   The monitor reports averages over set periods: an hour, a day, a week, a month or longer, depending on the model. Each model averages its data in its own way.

Two practical consequences follow. A monitor needs time before its first reading: from 90 minutes to 24 hours for the models C-NRPP approved. And short averages are less reliable than long ones: a few hours or days can read much lower or much higher than your real average. That is why the decision rests on the long-term average.

Learn what a monitor can and cannot do before you rely on it. In practice that means checking a handful of things, roughly in this order. None of them makes one monitor better than another for everyone; each decides whether a monitor fits your home and your question.

Chamber tests control the conditions. Two published field studies have run consumer monitors in real rooms beside a calibrated instrument. A 2024 study compared seven consumer models, including EcoQube, RadonEye, ViewPlus and WavePlus, with a calibrated AlphaGUARD over 54 days, and found each within 5% to 16% of the reference over the whole period. It also found response times of 1 to 15 hours, so a monitor's latest hourly figure can lag a real change. A 2026 study ran a Lüft beside a calibrated professional monitor in six rooms of a school in Utah for about 29 weeks and found a mean difference in 24-hour average radon of -0.05 pCi/L.

Neither study rates a brand, and neither covers every model sold today. Read together with C-NRPP's results, they point the same way: the averages of tested consumer monitors come close to a reference over weeks, and the long-term average, not the latest reading, is the number to trust. Full details are on independent accuracy results explained.

• Deciding on a few days of readings. Short-term measurements can be much lower or much higher than your average. Give it at least 3 months.
• Watching the hourly number. Radon varies from day to day and week to week, and some monitors react hours after a change. Read the long-term average.
• Testing the wrong room. Use a normal occupancy area on the lowest lived-in level, used at least 4 hours a day; not a kitchen, bathroom, laundry or storage room.
• Putting it in a draft. Keep it off the floor, away from exterior walls, vents, windows, fans, sunlight and electronic or network devices.
• Running out of memory. Some monitors store less than 3 months of data. Download or sync before it fills.
• Trusting an untested model. Check the evidence status and the recall list before you rely on any reading.

For a measurement that follows the Canadian protocol, one detector is enough. What matters is where that one goes: in a normal occupancy area of the lowest lived-in level, where someone spends more than 4 hours a day. U.S. guidance points to the same floor, the lowest lived-in level of the home.

Radon tests divide into passive devices, which need no power and go to a laboratory, and active devices, which need power and measure and record the radon in the air without a break. A consumer radon detector is a small active device. Both kinds can give a reliable answer; they suit different questions.

The instructions are short and clear: radon levels vary from day to day and week to week, a monitor should stay in place for at least 3 months, and the long-term average is the number to decide on. Where to put it, and how much of the test should fall in the heating season, come next.

1. 1Step 1 of 5:

   Put it in the right room

   A room occupied for at least 4 hours a day, on the lowest lived-in level of the home. Not a kitchen, bathroom, laundry or storage room.

2. 2Step 2 of 5:

   Put it in the right spot

   Off the floor, away from an exterior wall, out of direct sunlight and away from air currents from vents, doors, fans and windows, and away from electronic or network devices. See where to place a radon test.

3. 3Step 3 of 5:

   Run it through the heating season

   At least 3 months, preferably in the heating season. Canada's guidance asks for at least 91 days of the test to fall in the heating season.

4. 4Step 4 of 5:

   Ignore the hourly swings

   Short-term readings can be much lower or much higher than your average. Look at the trend, not the latest number.

5. 5Step 5 of 5:

   Decide on the long-term average

   If your monitor does not show one, read the maker's guide; each model averages differently. With less than 91 days of data, follow up with a long-term radon test.

Then compare the long-term average with the guidance levels. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L.

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2 pCi/L

4 pCi/L

00 Bq/m³274 Bq/m³4148 Bq/m³6222 Bq/m³8296 Bq/m³10+370 Bq/m³

• Below 2 pCi/L (below 74 Bq/m³)Below both of EPA's guidance levels.
• 2 to 4 pCi/L (74 Bq/m³ to 148 Bq/m³)EPA recommends considering a fix when the level is between 2 and 4 pCi/L.
• At or above 4 pCi/L (148 Bq/m³ and up)EPA recommends fixing a home when the radon level is 4 pCi/L or higher.

In a sale, a continuous monitor run for at least 48 hours is one of three accepted short-term options. Active devices can show unusual swings in the record, and some are designed to deter and detect test interference. You can also hire a qualified radon tester, very often a home inspector, who will use a device suited to your situation. Consumer monitors cannot be professionally calibrated, and C-NRPP does not approve them for use by radon measurement professionals.

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If you are testing in a real estate transaction and you need results quickly, any of the following three options for short-term tests are acceptable in determining whether the home should be fixed.

1. Option 1. Two tests at the same time

   Passive

   Take two short-term tests at the same time in the same location for at least 48 hours.

   What to do nextFix the home if the average of the two tests is 4 pCi/L or more.

   Two tests taken at the same time (simultaneous) would improve the precision of this radon test.

2. Option 2. One test, then a second

   Passive

   Take an initial short-term test for at least 48 hours. Immediately upon completing the first test, do a second test using an identical device in the same location as the first test.

   What to do nextFix the home if the average of the two tests is 4 pCi/L or more.

   One test followed by another test (sequential) would most likely give a better representation of the seasonal average.

3. Option 3. A continuous monitor

   Active

   Test the home with a continuous monitor for at least 48 hours.

   What to do nextFix the home if the average radon level is 4 pCi/L or more.

   Both active and passive devices may have features which help to prevent test interference.

Any real estate test for radon should include steps to prevent or detect interference with the test device. Your state radon office can help you decide which option is best.

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Radon detectors are sold by their makers and through retailers. A monitor in our list links to Amazon only once we have confirmed the listing is for that exact model, sold in the United States.

• Prices: we show a price only from the retailer's own product data, with the time it was checked, and hide it once that check is more than a day old. We never type a price into the page.
• Look-alikes: several recalled monitors look like ordinary small detectors. Match the brand and model number, not the photo, against our recall list.
• Units: check whether the monitor can show pCi/L, the unit U.S. guidance uses.

If you only need a first answer, a free kit may do. Free test kits are sometimes available from local or county health departments or from state radon programs, and kits can be bought from the National Radon Program Services at Kansas State University (1-800-SOS-RADON). See free radon test kits by state.

• Check the model against the recall list. Health Canada has recalled or warned about several monitors sold online; see recalled and not-approved radon monitors.
• Check the evidence status. A monitor with a C-NRPP result has been tested against a reference chamber. One without has not been tested by C-NRPP either way.
• Read the maker's accuracy claim for its conditions. A claim of, say, ±10% after 7 days at 200 Bq/m3 names a time and a level; compare like with like.