The EPA says radon is the second leading cause of lung cancer, and is responsible for about 21,000 lung cancer deaths each year. You can't see, smell or taste it. The EPA estimates that nearly 1 out of every 15 US homes has elevated radon. Testing is the only way to know your level.
Last updated: October 2026 · By the CleanAirHomeLab team
Quick Picks
Not sure what you need? Start with a test kit. If the result is 4 pCi/L or higher, the EPA says to fix your home. Between 2 and 4, it says to consider fixing. A monitor helps you watch your level over time.
What Is Radon?
The EPA says radon is a radioactive gas. It comes from the natural breakdown of uranium in soil, rock and water. It moves up through the ground and into your home through cracks and other holes in the foundation. Your home traps it inside, where it can build up.
The EPA estimates radon causes about 21,000 lung cancer deaths each year in the US. It says radon is the number one cause of lung cancer among non-smokers, and the second leading cause overall.
4 pCi/L
EPA Action Level
EPA: fix your home at or above this level
2 to 4 pCi/L
Consider Fixing
EPA: consider fixing your home in this range
1.3 pCi/L
US Indoor Average
EPA estimate of the average indoor radon level
The EPA and the Surgeon General recommend testing all homes below the third floor.The EPA says radon levels can vary greatly from home to home. A neighbor's low reading does not tell you yours.
Test Kit vs. Monitor: Which Do You Need?
There are two ways to test for radon. A test kit gives you one result from a lab. A monitor keeps reading as long as it runs. The EPA says a short-term test is less likely than a long-term test to show your year-round average. Here is how the picks on this page compare.
Type
How long it reads
Keeps reading
Best For
Short-term charcoal kit (First Alert RD1)
2 to 4 days, then mail to the lab
No
A quick first check
Long-term alpha track kit (RadonAway)
91 days to 1 year, then mail to the lab
No
A year-round average
Radon monitor with a screen (Corentium Home 2)
First average after one full day
Yes, works without an app
Watching your level at a glance
Wi-Fi radon monitor (View Radon)
Continuous
Yes, over Wi-Fi
Checking from your phone
Multi-sensor monitor (Wave Plus)
Continuous
Yes, over Bluetooth
Radon plus CO2, TVOC, humidity, temperature and air pressure
Our take: Start with a test kit for a baseline. If you fix your home, the EPA says to test again afterward to be sure the level came down. A monitor makes that easy to watch.
Six sensors in one: radon, CO2, TVOC, humidity, temperature and air pressure. It runs on 2 AA batteries.
Key Specs
Sensors
Radon, CO2 (NDIR), TVOC, humidity, temperature, air pressure. No particulate sensor.
CO2 Range
400-5,000 ppm
Power
2x AA, about 16 months over Bluetooth
Connectivity
Bluetooth or Airthings SmartLink (hub required for continuous cloud sync)
What We Like
Tracks radon, CO2 and TVOC in one device
Runs on 2 AA batteries, about 16 months on Bluetooth
CO2 is measured with an NDIR sensor, 400 to 5,000 ppm
What Could Be Better
No particulate sensor, so it cannot track particles
Needs an Airthings hub for continuous cloud sync
Our Verdict
The Wave Plus does more than radon. It also tracks CO2, TVOC, humidity, temperature and air pressure. It runs on AA batteries. If you only need radon, a radon-only monitor or a test kit covers that.
Digital radon monitor. It also reads temperature and relative humidity. It runs on 2 AA batteries and has an LCD with six views.
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
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
LCD with six views
Works standalone, without the app
Runs on 2 AA batteries for up to 3 years
Radon range is 0 to 250 pCi/L, accurate to within 10%
Free 5-year warranty when registered within 30 days
What Could Be Better
The first average shows after one full day of data
The 5-year warranty needs registration within 30 days
Our Verdict
The Corentium Home 2 is a digital radon monitor that works without an app. It shows radon, temperature and humidity on its LCD. It runs on 2 AA batteries for up to 3 years. The first average shows after one full day.
Runs on 6 AA batteries or USB, up to 3 years on batteries
What Could Be Better
Radon, humidity and temperature only. No PM2.5, CO2 or VOC
Our Verdict
The View Radon tracks radon, humidity and temperature. It has built-in Wi-Fi and an e-paper display. It measures no PM2.5, CO2 or VOC. The Wave Plus has more sensors.
Long-term alpha track radon test. Leave it out for 91 days to 1 year, then mail it in. Lab analysis is included.
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
Includes
One detector, lab analysis and a return USPS mailer
What We Like
Long-term test: 91 days to 1 year
Analysis by an accredited radon laboratory is included
A return USPS mailer is included
What Could Be Better
The test takes at least 91 days
Results usually take 2 to 4 weeks after the lab gets it
It is not a charcoal canister. RadonAway sells that as a separate short-term test
Our Verdict
The RadonAway Alpha Track is a long-term radon test. You leave it out for 91 days to 1 year, then mail it to the lab. Results usually come 2 to 4 weeks after the lab gets it. The EPA radon action level is 4 pCi/L.
Passive charcoal radon test kit that you mail in. It is not an electronic detector. Leave it out for 2 to 4 days. Lab fees are included, except New Jersey state fees.
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 level of your home
Lab Analysis
Included in the purchase price (excludes New Jersey state fees)
Result Time
3 to 5 business days after the lab receives it
EPA Listing
Listed under the EPA Radon Gas Measurement Proficiency Program
What We Like
Short test: 2 to 4 days
Lab fees are included, except New Jersey state fees
Results come 3 to 5 business days after the lab gets it
Listed under the EPA Radon Gas Measurement Proficiency Program
What Could Be Better
Not an electronic detector. No display, no battery and no alarm
New Jersey state fees are not included
Our Verdict
The First Alert RD1 is a charcoal test kit, not a digital monitor. You leave the sampler on the lowest level of your home for two to four days, then mail it in. Results come 3 to 5 business days after the lab gets the kit. It has no display, no battery and no alarm.
The EPA says to fix your home if the radon level is 4 pCi/L or higher. Between 2 and 4 pCi/L, the EPA says to consider fixing it. The EPA estimates the average indoor level at about 1.3 pCi/L, and about 0.4 pCi/L outdoors. The EPA also says no level of radon is safe, and levels below 4 pCi/L still pose some risk.
How long does a radon test take?+
The EPA says short-term tests stay in your home for 2 days to 90 days, and long-term tests stay more than 90 days. A long-term test is more likely to show your year-round average. If you need results fast, the EPA says a short-term test followed by a second short-term test may be used to decide whether to fix your home. For a home sale, the EPA says the result of two short-term tests can be used.
Do all homes need a radon test?+
The EPA and the Surgeon General recommend testing all homes below the third floor. The EPA says any home may have a radon problem: new and old homes, well-sealed and drafty homes, and homes with or without basements. Radon comes from uranium in nearly all soils. It gets in through cracks and other holes in the foundation. The EPA says radon levels can vary greatly from home to home, so a neighbor's result does not tell you yours.
What is the difference between a radon test kit and a radon monitor?+
A test kit gives one result. You leave it out, then mail it to a lab. A charcoal kit like the First Alert RD1 sits out for 2 to 4 days. An alpha track kit like the RadonAway sits out for 91 days to 1 year. A radon monitor is an electronic device that keeps reading. It suits people who want to watch their level over time, such as after a fix.
How is radon fixed, and what does it cost?+
The EPA says the main method is a vent pipe and fan that pulls radon from under the house and vents it outside. This is called soil suction. The EPA says some systems can cut radon levels by up to 99%. It says most homes can be fixed for about the same cost as other common home repairs, and to get estimates from qualified mitigators. The EPA guide gives no dollar figure.
Where should I put a radon test kit?+
The EPA says to put it in the lowest lived-in level of the home, in a room you use often, but not the kitchen or bathroom. Place it at least 20 inches above the floor, away from drafts, high heat, high humidity and outside walls. For a short-term test, keep windows and outside doors closed as much as you can. For a 2 or 3 day test, close them at least 12 hours before you start.
Want the Full Air Quality Picture?
Radon is one reading. See our picks for air quality monitors that also track PM2.5, CO2 and VOCs.
This page is general information, not medical advice. Health figures on this page are the EPA's.
Affiliate Disclosure: Some links on this page are Amazon affiliate links and may earn us a commission at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. Airthings, First Alert and RadonAway do not pay us. Our picks are based on published specs and sensor type, 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 .
