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Choose an electronic radon monitor with both short-term and long-term averages, a stated accuracy that improves with time (about ±10 percent at 30 days is typical of good consumer units), and a display or app you will actually look at. Place it in the lowest occupied floor, in a room where people spend time, away from drafts and the sump. Run it for at least 90 days including a heating season before judging against the action level (100 Bq/m³ WHO, 4 pCi/L US EPA). Use a laboratory alpha-track detector when a certified result is needed for a sale or a dispute.
Types
| Type | How it works | Best for | Limits |
|---|---|---|---|
| Charcoal canister (lab) | Adsorbs radon for 2 to 7 days; lab counts it | Quick screening | Short window; sensitive to humidity; can miss seasonal highs |
| Alpha-track detector (lab) | Plastic records alpha hits over 90 days to a year; lab etches and counts | Certified long-term average; transactions | No live reading; one number at the end |
| Consumer electronic monitor | Diffusion chamber with an alpha detector; rolling averages | Ongoing monitoring; seasonal patterns; mitigation checks | Noisy first week; not certified for transactions in most places |
| Professional continuous monitor | Ion chamber or pulsed detector; hourly data; tamper detection | Real estate transactions where required; diagnostics | Cost; usually rented with a technician |
What to check on an electronic monitor
- Averages shown: short-term (1 to 7 days) and long-term (30 days to 1 year). See short-term vs long-term radon readings.
- Stated accuracy versus time: for example ±20 percent at 7 days, ±10 percent at 30 days.
- Units: Bq/m³ and pCi/L, switchable.
- Power: battery (Airthings Corentium Home 2 runs years on AA) or mains.
- Connectivity: standalone display (Corentium) or app and dashboard (Airthings View Radon, Aranet Radon Plus, View Plus).
- Extras: temperature, humidity and pressure help interpret swings; a full air quality monitor adds CO₂ and particles.
- Alerts: at a long-term threshold, not a daily one.
Placement
- Lowest level that is lived in: a basement bedroom or family room, or the ground floor.
- A room used for hours a day, not a laundry or garage.
- 0.5 to 2 m above the floor, on a shelf or table.
- Away from exterior doors, windows, vents, fans, the sump and crawl-space hatches.
- Not in direct sun or high humidity.
- Leave it there; moving it resets the average.
Reading the result
Ignore the first week. Judge by the 30-day and longer figures, and keep monitoring through a winter. Compare against the action level for your country. Confirm a high long-term reading with a laboratory test before commissioning mitigation, and keep the electronic monitor running afterward to prove the fix. See what radon is and why long-term monitoring matters.
Which to buy
- Standalone, battery, no app: Airthings Corentium Home 2.
- Connected radon only: Airthings View Radon, Aranet Radon Plus.
- Radon plus full air quality: Airthings View Plus.
- Certified result: a laboratory alpha-track kit from an accredited provider.
Combination monitors are compared in best air quality monitors; for the whole-home picture see how to build a whole-home monitoring setup.
Recommended Tools
Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.
Frequently Asked Questions
Are electronic radon monitors accurate?
Good ones state about ±10 percent after 30 days at moderate levels and improve with longer averaging. Their first week is noisy by design; judge by the long-term figure.
Should I buy a monitor or do a lab test?
Both have a place. A laboratory alpha-track test over 90 days gives a certified average for a transaction. An electronic monitor gives ongoing readings, shows seasonal swings, and verifies mitigation.
Where should the radon monitor go?
In the lowest level that is lived in, in a bedroom or living space rather than a utility area, at 0.5 to 2 m height, away from drafts, windows and the sump.
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