Radon is the second leading cause of lung cancer in the US, responsible for 21,000 deaths per year according to the EPA. It is colorless, odorless, and already in your home right now. The EPA says 1 in 15 American homes has radon above the action level of 4 pCi/L. Most homeowners have never tested.
Last updated: April 2026 · By the CleanAirHomeLab team
Quick Picks
Not sure what you need? Start with the $15 test kit. If it reads above 2 pCi/L, buy a continuous monitor. Here are our picks for every scenario.
What Is Radon?
Radon is a naturally occurring radioactive gas that forms when uranium breaks down in soil and rock. It seeps up through the ground and enters your home through foundation cracks, floor drains, sump pits, and gaps around pipes. Once inside, it can build up to dangerous levels, especially in basements and lower floors where ventilation is limited.
When you breathe radon, it decays into radioactive particles that can lodge in your lungs and damage cells over time. The EPA estimates radon causes about 21,000 lung cancer deaths each year in the US, more than drunk driving, drowning, and home fires combined. It is the #1 cause of lung cancer in non-smokers.
4 pCi/L
EPA Action Level
Fix your home if your reading is at or above this level
2–4 pCi/L
Consider Mitigation
Risk is present. Mitigation is recommended but not mandatory
1.3 pCi/L
US Average
Average indoor radon level across American homes
The EPA says every home should be tested, regardless of location, age, or construction type. Homes that look identical can have vastly different radon levels. Your neighbor having a low reading tells you nothing about yours.
Test Kit vs. Monitor, Which Do You Need?
There are two ways to test for radon. A test kit gives you a one-time result for $15. A monitor gives you continuous readings for $79–$229. Here is how to choose.
Type
Cost
Accuracy
Ongoing
Best For
Short-term test kit (48–96h)
$10–20
Low (snapshot)
No
Quick check, curious homeowners
Long-term test kit (90 days)
$15–30
High (averaged)
No
First test, real estate transactions
Digital alarm (First Alert)
$70–80
Moderate
Yes + audible alarm
Simple always-on alert device
Radon-only monitor (Corentium)
$150–200
High (long-term avg)
Yes
Ongoing peace of mind, no app needed
WiFi monitor (View Radon)
$199
High
Yes + remote alerts
Remote monitoring, app users
Multi-sensor monitor (Wave Plus)
$229
High
Yes + 5 other sensors
Full air quality picture
Our recommendation: Start with the long-term test kit. It costs $15 and gives you an accurate baseline. If the result is above 2 pCi/L, buy a continuous monitor to track your levels after any mitigation work.
Full Reviews
#1 Best Overall
Airthings Wave Plus
Check current price
Six sensors in one: radon, CO2, VOCs, humidity, temperature, and air pressure. Battery-powered and wall-mountable anywhere — including your basement.
Key Specs
Sensors
Radon, CO2 (NDIR (non-dispersive infra-red)), TVOCs, Humidity, Temperature, Air Pressure
Radon Range
0–500+ pCi/L
CO2 Range
400–5,000 ppm
Power
2x AA batteries (~16 months)
Connectivity
Bluetooth (optional Airthings Hub for WiFi)
Display
None (wave-to-read LED: green/yellow/red)
Accurate After
7 days
Dimensions
4.7 in diameter × 1.4 in deep
Warranty
1 year
What We Like
Tracks radon AND CO2 AND VOCs — the only 6-in-1 consumer monitor
Battery-powered (2x AA) — mount in basement without needing an outlet
Wave your hand to get a color-coded radon reading in seconds
Free Airthings app with long-term trend history and alerts
Radon readings are EPA-accepted for residential use
What Could Be Better
No PM2.5 sensor — cannot track fine particle pollution
Radon takes at least 7 days to show a reliable reading
Bluetooth only — needs to be within 10 feet of your phone to sync
No built-in display — reading requires the app or wave gesture
CO2 reading is an estimate, not direct NDIR measurement
Our Verdict
The Airthings Wave Plus is overkill if all you need is radon. But it is the right choice if you want to understand your whole indoor air picture. Six sensors for $229 is genuinely good value. The radon reading alone justifies the price for most homeowners who have never tested, so you find out whether the basement your kids play in is safe before spending $1,500 on mitigation. If you just need a quick one-time result, the $15 RadonAway test kit is more practical.
Radon-only digital monitor. Three AA batteries. Displays 24-hour, 7-day, and long-term averages right on the screen — no phone needed.
Key Specs
Sensors
Radon, temperature and relative humidity
Radon Range
0-250 pCi/L (0-9,999 Bq/m3), accurate to within 10%
Detection Method
Alpha spectrometry
Display
LCD with six views: 24-hour, 7-day, 30-day and long-term averages up to one year, plus temperature and humidity
Power
2x AA, up to 3 years of battery life
Connectivity
Bluetooth to the Airthings app, plus Airthings SmartLink. Works standalone without the app.
First Reading
First average appears after one full day of data
Warranty
Free 5-year warranty when registered within 30 days
What We Like
Digital display shows 24h, 7-day, and long-term radon averages at a glance
No app required — readings are always visible on the device
Runs on 3 AA batteries for up to 18 months
Lightweight at 3.5 oz — easy to move between floors for testing
4.4-star average across thousands of Amazon reviews
What Could Be Better
Radon only — no other air quality sensors
No WiFi or app connectivity — readings are display-only
Still takes 7+ days for a stable long-term reading
No alert system — you have to remember to check the display
Older design compared to the View Radon
Our Verdict
The Corentium Home 2 is the best radon monitor for people who want a simple, reliable device with no app dependency. It replaced the original Corentium Home, which Airthings no longer sells. You put it in the basement, check the display once a week, and you are done. At $149, it costs $50 more than the test kit but gives you continuous monitoring instead of a one-time snapshot. That is worth it for most homeowners.
2.9 inch e-paper plus a red/yellow/green glow ring
Power
6x AA or USB, up to 3 years on batteries
Connectivity
WiFi 2.4 GHz, Airthings SmartLink, Bluetooth LE
Accurate After
7 days
Dimensions
17 x 9 x 3.3 cm (6.7 x 3.5 x 1.3 in)
Warranty
1 year, optional 5-year extension
App
Free (iOS + Android)
What We Like
WiFi built in — no separate hub needed to get data to your phone
E-ink display is always on, shows current readings without power draw
Automatic cloud sync means you can check radon levels remotely
Tracks humidity and temperature alongside radon
Clean, modern design — looks good on a shelf or bookcase
What Could Be Better
Only 3 sensors (radon, humidity, temp) — less than the Wave Plus
E-ink display is small and hard to read from across the room
At $199, it costs $50 more than the Corentium for similar radon data
Cloud-dependent — requires active Airthings account
Battery life shorter than the Corentium due to WiFi radio
Our Verdict
The Airthings View Radon sits in an awkward middle spot. It costs more than the Corentium Home 2 but measures fewer things than the Wave Plus. Its main edge is built-in WiFi — no hub required, automatic app sync. If you want to monitor your basement radon remotely from your phone, this is the cleanest way to do it. Otherwise, the Corentium saves you $50.
90-day charcoal canister test kit. Mail it in, get EPA-accepted lab results. The cheapest way to find out if your home has a radon problem.
Key Specs
Type
Alpha track long-term detector. NOT a charcoal canister; RadonAway sells those separately as a short-term test.
Test Duration
91 days to 1 year
Lab Analysis
Included, by an accredited radon laboratory. Return USPS mailer supplied.
Result Time
Usually 2 to 4 weeks after the laboratory receives it
Result Format
Mailed report + email (pCi/L)
EPA Accepted
Yes
Real Estate Use
Yes (long-term only)
Detection Range
0.1–100+ pCi/L
Includes
Canister, instructions, prepaid return envelope
What We Like
At $15, it is the lowest-cost way to get an accurate radon reading
Lab analysis is included in the price — no extra fees
EPA-accepted results — usable for real estate transactions
90-day exposure gives a more accurate long-term average than short tests
No setup, no app, no WiFi — just place it and wait
What Could Be Better
One-time snapshot — you only know what radon was during those 90 days
Must mail in and wait for lab results (1-2 weeks after mailing)
Does not give ongoing monitoring or alerts
Seasonal variation can affect accuracy (radon is higher in winter)
You need to remember to mail it after 90 days
Our Verdict
The RadonAway test kit is the right starting point for anyone who has never tested their home. Fifteen dollars and 90 days tells you whether you have a problem. If the result comes back under 2 pCi/L, you are fine. If it reads above 4 pCi/L, you need mitigation and should buy a continuous monitor to track the fix. Do this test before spending $150+ on a monitor.
Battery-powered digital radon alarm. Continuous monitoring with LED display. Sounds an alarm if radon exceeds EPA action level. Budget always-on option.
Key Specs
Type
Passive charcoal short-term test kit. Not an electronic detector: no display, no battery, no alarm.
Test Duration
Leave the sampler out for 2 to 4 days on the lowest lived-in level
Lab Analysis
Included in the purchase price (excludes New Jersey state fees)
Result Time
3 to 5 business days after the lab receives it
Result Format
pCi/L, reported by the laboratory
EPA Listing
Listed under the EPA Radon Gas Measurement Proficiency Program
Units
picoCuries per litre of air (pCi/L)
Region
For use within the United States
What We Like
At $79, the cheapest continuous radon monitor on the market
Audible alarm triggers if radon exceeds 4 pCi/L action level
Battery-powered — plug it in or use batteries, works anywhere
LED display shows current radon level at a glance
First Alert is a trusted brand known for home safety devices
What Could Be Better
3.8-star rating reflects accuracy complaints from some users
No app, no WiFi, no data history — just the current reading
The alarm threshold is fixed at 4 pCi/L — not adjustable
Less sensitive sensor than Airthings devices
No CO2, VOC, or humidity sensors — radon only
Our Verdict
The First Alert RD1 is for people who want a plug-in alarm that goes off if radon gets dangerous — similar to how a smoke detector works. For that job, it is fine. But if you want accurate trend data, long-term averaging, or any data logging, step up to an Airthings. The 3.8-star rating is worth noting — some users report readings that disagree with lab tests. Treat this as an alert device, not a precision instrument.
The EPA sets the action level at 4 pCi/L. At that level, the EPA recommends fixing your home. If your reading is between 2 and 4 pCi/L, the EPA recommends considering mitigation, the risk is lower but real. Average indoor radon level in the US is about 1.3 pCi/L, and outdoor air is roughly 0.4 pCi/L.
How long does a radon test take?+
Long-term tests (90 days) give the most accurate reading because they average out daily and seasonal fluctuations. Short-term tests (48–96 hours) are faster but less reliable, radon levels can swing significantly based on weather, barometric pressure, and whether windows were open. For buying or selling a home, a short-term test is usually accepted. For personal peace of mind, do the 90-day test.
Do all homes need a radon test?+
Yes. The EPA recommends testing every home regardless of location, construction type, or age. Radon comes from uranium decay in soil and enters through foundation cracks, floor drains, and sump pits. Even new construction can have high radon. The only way to know is to test. Ground-floor and basement spaces have the highest levels.
What is the difference between a radon test kit and a radon monitor?+
A test kit is a one-time snapshot. You place a charcoal canister for 90 days, mail it to a lab, and get a result. A radon monitor is a continuous electronic device that tracks radon levels over time. Test kits are cheaper and give EPA-accepted results for real estate transactions. Monitors are better for ongoing awareness after mitigation, or for people who want to watch their levels change over time.
How much does radon mitigation cost?+
Most homes can be mitigated with a sub-slab depressurization system. A contractor installs a pipe through the foundation slab and a fan that pulls radon from under the house before it enters. Cost ranges from $800 to $2,500 depending on your foundation type, home size, and local contractor rates. The average is around $1,200. Once installed, the fan runs continuously and typically drops radon levels by 50–99%.
Does opening windows lower radon?+
Yes, temporarily. Increased ventilation dilutes radon and can drop levels while windows are open. But this is not a practical solution, you cannot keep windows open year-round in most climates, and levels rebound when you close them. Only proper sub-slab mitigation provides a permanent fix. Use ventilation as a short-term measure while you wait for a contractor, not as a long-term strategy.
Want the Full Air Quality Picture?
Radon is one piece. PM2.5, CO2, and VOCs affect your daily health too. See our picks for the best air quality monitors that cover all four.
Affiliate Disclosure: Some links on this page earn commissions at no extra cost to you. Our picks are based on testing data and sensor accuracy, not commission rates. Full disclosure.
Sources and last review
Specifications on this page are taken from the documents below, on the dates shown. We do not physically test products; read our methodology. Page last reviewed .
