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Radon test kits: every kit compared, unranked
Short answer
A radon test kit is a passive device that sits in your home for a set time and is then mailed to a laboratory, which reports your average radon level. Use a short-term kit first for a quick answer, then a long-term kit or a second short-term kit to confirm a high result.
Key takeaways
- A radon test kit is a passive device: it needs no power, sits in your home for a set time, and is then mailed to a laboratory that works out your average radon level.
- There are four kinds: charcoal canisters, charcoal liquid scintillation devices, alpha track detectors and electret ion chambers. All four are generally inexpensive.
- Short-term kits stay in the home for 2 to 90 days, depending on the device, and never less than 48 hours. Long-term kits stay for more than 90 days and give a better picture of your year-round average.
- The first step for most homes is a short-term test. If the result is at or above 4 pCi/L, a follow-up test confirms it before you decide on a fix.
- Free kits are sometimes available from state radon programs and local health departments. See free radon test kits by state.
What a radon test kit is
A radon test kit is a low-cost way to find out how much radon is in the air of your home, and there are many kinds of do-it-yourself kit. They work without power: the device sits open to the air in your home for a set time, then goes to a laboratory for analysis. You can buy them in hardware, drug and other stores, or order them by mail or phone. The laboratory, not the kit, produces the number, so a kit is only as good as the lab that reads it and the care taken while it was in the house.
This hub covers every kind of kit, every kit we have verified with its maker, how to choose between them, how to run a test so the result can be trusted, where to get one free, and what to do with the result. Everything is unranked: we list kits in a neutral order that is printed above the list, and we never name one kit as the one to buy. If you want a device that shows a running reading instead of a mailed-off sample, see radon detectors and monitors.
- Passive radon test
- A test device that needs no power. It collects a record of radon over a set exposure time and is then analyzed by a laboratory. Charcoal canisters, alpha track detectors, charcoal liquid scintillation devices and electret ion chambers are all passive devices.
- 48 hours
- The shortest any radon test should run, kit or professional.
- 2 to 90 days
- A short-term test, depending on the device. Most charcoal kits take 2 to 7.
- Over 90 days
- A long-term test, the closer estimate of your year-round average.
Every radon test kit we cover
The list below holds every short-term and long-term kit we have verified against its maker's own page, with how each one measures, how long it stays in the home, whether the lab fee is in the price and how the result reaches you, as the maker states them. A kit is added once its model, U.S. availability and lab details have been confirmed and dated. A kit without a shopping link is still listed if it is credible. How we decide what to include is set out on how we cover products.
Each figure is the maker's own, as its product page or manual states it.
Short-term test kits (3)
- First Alert RD1
- How it measures
- Activated charcoal (activated carbon), laboratory analysis
- Time in the home
- 2 to 4 days
- Lab fee in the price
- Included
- Result
- pCi/L, in the laboratory report
- Kidde 442020
- How it measures
- Activated charcoal sampler, laboratory analysis
- Time in the home
- 3 days
- Lab fee in the price
- Included
- Result
- Not stated
- PRO-LAB RA100
- How it measures
- Liquid scintillation detectors with silica gel desiccant, laboratory analysis
- Time in the home
- 96 hours
- Lab fee in the price
- Separate
- Result
- pCi/L
The four kinds of radon test kit, and how each one works
Charcoal canisters, alpha track, electret ion chamber, continuous monitors and charcoal liquid scintillation detectors are the devices most commonly used for short-term testing, and alpha track and electret detectors are commonly used for long-term testing. The four that come as mailed kits work in quite different ways:
| Kind | How it records radon | How long it usually runs | What happens at the lab |
|---|---|---|---|
| Activated charcoal canister | Activated carbon, which binds gases strongly, absorbs radon from the room air | Short-term: 2 to 7 days depending on the maker; some need a longer minimum, such as a 7-day charcoal canister | The kit is resealed and returned; the lab measures what the charcoal collected |
| Charcoal liquid scintillation | Its own kind of passive device | Short-term | Analyzed by a laboratory, like a charcoal canister |
| Alpha track detector | A thin plastic film inside a filtered chamber. Alpha particles from radon and its decay products strike the film and leave tracks; the number of tracks correlates with the integrated radon level | Mostly long-term. Usually 100 to 120 days; long-term tests run from 3 months to 1 year | An etching process makes the tracks visible, and they are counted |
| Electret ion chamber | A small plastic chamber with a charged disk (the electret). Radiation from radon ionises the air inside and lowers the disk's voltage | Short-term or long-term, depending on the electret type | The drop in voltage over a known time is read with calibrated readers. The detectors are not destroyed, so they can be reused |
Charcoal kits: the common short-term test
Most kits sold for a first test are activated charcoal. They come in various forms, all using activated carbon to absorb radon gas, with exposure times between 2 and 7 days depending on the maker; after exposure they are resealed and returned to a laboratory. Record the start and stop times and the test location on the form, so the lab can report the result for the period the kit was open.
Alpha track kits: the common long-term test
An alpha track detector holds a thin plastic "foil" in a container. Alpha particles from radon and its decay products leave tracks in it, and at the laboratory an etching process makes those tracks visible so they can be counted. The number of tracks correlates with the integrated radon level over the test period. Finish the test before the expiry date printed on the package. This is the kit to use when you want your year-round average rather than a quick answer.
Electret kits: short or long, and reusable
An electret ion chamber measures the drop in voltage on a charged disk over a known time. It can be used for short-term or long-term measurements depending on the electret type, the reader is calibrated, and the detector is not destroyed in the process.
Short-term or long-term: which kit to use first
EPA sets out an order of testing for most homes. Step 1 is to take a . If the result is at or above 4 , Step 2 is to follow up with either a or a second short-term test: a long-term test for a better understanding of your year-round average, or a second short-term test if you need results quickly. The higher the first result, the more certain you can be that a short-term follow-up is the right choice.
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1Step 1: Take a short-term test.
- Below 4 pCi/LEven if your test result is below 4 pCi/L, you may want to test again sometime in the future.
- At or above 4 pCi/LIf your result is at or above 4 pCi/L, take a followup test to be sure.
2Step 2: Follow up with either a long-term test or a second short-term test.
- Long-term testFor a better understanding of your year-round average radon level, take a long-term test.
- Second short-term testIf you need results quickly, take a second short-term test. If your first short-term test result is more than twice EPA's 4 pCi/L action level, you should take a second short-term test immediately.
3Step 3: Decide whether to fix your home.
- After a long-term testFix your home if your long-term test result is 4 pCi/L or more.
- After a second short-term testConsider fixing your home if the average of your first and second test is at or above 4 pCi/L.
| Compared | Short-term kit | Long-term kit |
|---|---|---|
| How long it stays in the home | 2 to 90 days depending on the device, never less than 48 hours | More than 90 days; usually 3 months to 1 year |
| Usual devices | Charcoal canister, charcoal liquid scintillation, electret | Alpha track, electret |
| What it tells you | A first answer, quickly | A result more likely to reflect your year-round average |
| House rules during the test | Closed-house conditions; for tests under four days, from 12 hours before | Live normally |
| Used for | A first test, a follow-up when you need speed, a home sale | Confirming a short-term result, deciding on a fix with time to spare |
Why not always test long? Because radon matters most when you know about it, and a short-term kit gives a first answer in under a week. Why not always test short? Because radon levels tend to vary from day to day and season to season, so a short-term test is less likely to tell you your year-round average. A worked example shows the uncertainty: if the average of two short-term tests is 4.1 pCi/L, there is about a 50 percent chance that the year-round average is somewhat below, or above, 4 pCi/L.
How to choose a radon test kit
Every kit we list measures radon; the differences are in what you need the answer for, how soon, and what the price covers. These are the questions that separate one kit from another, with the reason each one matters:
| Question | Why it matters | Where to find the answer |
|---|---|---|
| Is it short-term or long-term? | It decides whether you get a quick first answer or a year-round average | The package and the maker's page |
| How long must it stay out? | Some devices need more than the 48-hour minimum, such as a 7-day charcoal canister | The instructions |
| Does the price include the lab's analysis and return postage? | The lab produces the result; a kit with a separate lab fee costs more than its shelf price | The maker's page; our list shows it as the maker states it |
| Which laboratory reads it? | Use a radon measurement device from a qualified laboratory; your state may list do-it-yourself devices from qualified labs | The package; your state radon program |
| How fast are results? | Results take a few days or weeks; if you need them quickly, find out how long and request expedited service | The lab's instructions |
| Is there an expiry date? | Finish an alpha track test before the maker's expiry date | The package |
| Is it for a home sale? | A sale needs steps to prevent or detect interference, and often two kits | See testing for a home sale below |
How to use a radon test kit, step by step
Read the instructions and the dates
Note the minimum and maximum exposure time and any expiry date. Plan to post the kit back the day the test ends.
Close up the house if the test is short
Keep windows and outside doors closed except for normal entry and exit. For a test lasting less than four days, close them at least 12 hours before you start. Heating and air conditioning fans that recirculate air may run; fans that bring in air from outside should not.
Choose the room
The lowest level of the home that could be used regularly, finished or not: a living room, playroom, den or bedroom. Not a kitchen, bathroom, laundry, closet, stairway, hallway or crawl space.
Place the kit
At least 20 inches above the floor, where it will not be disturbed, and away from drafts, high heat, high humidity and exterior walls.
Start the test and record it
Open the kit as the instructions say and write down the start date and time. Avoid short tests of under four days during severe storms or high winds.
End the test and seal the kit
At the end of the exposure time, record the stop date and time, reseal the package and complete the form, including where in the house it was.
Post it to the lab promptly
Send it right away. Results usually take a few days or weeks.
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| Test | How long it runs | What it is for |
|---|---|---|
| Short-term test | Stays in the home from 2 to 90 days, depending on the device, and for a minimum of 48 hours. | A faster screening result. Because radon levels vary from day to day and season to season, it is less likely than a long-term test to tell you the year-round average. |
| Long-term test | Stays in the home for more than 90 days. | It is more likely than a short-term test to tell you the home's year-round average radon level. |
| Continuous monitor | Logs readings for the whole test, run as a short-term or a long-term test under the same durations in EPA guidance. | Logs a graph over time, so you can see trends and spot anomalies rather than a single number. |
For more on choosing a spot, see where to place a radon test. For what can push a reading up or down, see what can affect a radon test.
Do it yourself, or hire a tester?
A test kit is designed to be used by anyone. If you prefer, or if you are buying or selling a home, you can hire a qualified tester to do the testing for you; your state radon office can give you a list of qualified testers. You can also contact a private radon proficiency program for lists of privately certified radon professionals serving your area.
| Compared | Do-it-yourself kit | Qualified radon tester |
|---|---|---|
| Who places the device | You, following the kit's instructions | The tester, who picks the location for the space's intended use |
| Devices | Passive kits from a qualified laboratory | Any passive device, or a continuous monitor |
| Closed-house conditions | You keep them | The tester explains them and documents the test |
| Report | From the laboratory | From the tester, including the analysis of the data |
| Suits | Your own home, a first answer, a long-term average | Home sales, results others will rely on |
To find one, see radon professionals, or your state radon program.
Free and low-cost radon test kits
You may not need to buy a kit at all. Free test kits are sometimes available from local or county health departments or from state radon programs, and some local programs hand them out free or at reduced cost. The National Radon Program Services at Kansas State University sells kits online and by phone at 1-800-SOS-RADON (1-800-767-7236). Kits are also available from some local or state American Lung Associations and some home improvement stores. State programs that hand out kits generally do not favor one maker or laboratory over another.
- Check your state first. Our free radon test kits by state page lists the state programs that give out kits and who qualifies.
- Watch for January offers. January is National Radon Action Month, and some states give out free kits then: Pennsylvania announced free kits from the American Lung Association on 2 January 2024, and North Carolina, in a notice of 30 December 2025, offered free kits from January, each while supplies lasted.
- Ask your state radon office for its list of do-it-yourself devices from qualified laboratories. Find it on state radon programs.
What to do with your result
The lab reports your result in picocuries per liter (pCi/L). 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. If your first short-term result is high, follow the steps above and confirm it with a long-term or second short-term test before deciding. The results interpreter explains any number, and radon levels explains the scale.
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- 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.
Even if your result is below 4 pCi/L you may want to test again sometime in the future, and you should retest if you begin occupying a lower level of your home or after you renovate. If you fix a high level, retest at least every two years; see radon mitigation.
Your result
Got a number back from the lab?
Read it against the two guidance levels, then decide whether you need a second test or a fix.
- What your pCi/L figure means
- When a second test comes first
- What a fix involves
- How often to test again
Test kits for a home sale
A test for a home sale has to be quick and hard to tamper with. EPA accepts three short-term options when results are needed quickly: two passive tests at the same time, two passive tests one after the other with identical devices, or a continuous monitor for at least 48 hours. There is a potential for test interference in real estate transactions, and that some passive devices offer more resistance to interference than others.
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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.
Option 1. Two tests at the same time
PassiveTake 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.
Option 2. One test, then a second
PassiveTake 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.
Option 3. A continuous monitor
ActiveTest 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.
In many cases buyers and sellers decide to have the test done by a qualified radon tester, who can also explain how will be kept. Your state may set its own rules. For the whole process, see buying a house with radon and selling a house with radon.
Radon questions people ask about test kits
Which radon test kit should I buy?
We do not rank kits. Any kit analyzed by a qualified laboratory and used as its instructions say can give a reliable result. Choose by what you need: a short-term charcoal kit for a quick first answer, a long-term alpha track kit for your year-round average. Every kit we have verified is in the list above.
How do radon test kits work?
The kit collects a record of radon while it sits in your home: charcoal absorbs the gas, an alpha track film records particle tracks, or an electret loses charge. You then seal it and mail it to a laboratory, which works out the average level over the test.
How long does a radon test kit take?
A short-term kit stays out for 2 to 90 days depending on the device, never less than 48 hours; most charcoal kits run 2 to 7 days. A long-term kit stays more than 90 days. Lab results then take a few days or weeks.
Are home radon test kits accurate?
They can be, when they come from a qualified laboratory and are used as instructed. Improper testing can give an inaccurate result: open windows during a short test, a bad spot or a late return to the lab can all mean testing again.
Short-term or long-term radon test: which should I do first?
The first step is a short-term test. If the result is at or above 4 pCi/L, follow up with a long-term test, or a second short-term test if you need results quickly.
Where should I put a radon test kit?
In the lowest level of the home that could be used regularly, in a room such as a living room or bedroom, at least 20 inches above the floor, away from drafts, heat, humidity and exterior walls. Not in a kitchen, bathroom, laundry, closet or crawl space.
Do I need to keep windows closed during a radon test?
Yes, for a short-term test: keep windows and outside doors closed except for normal entry and exit, and for a test under four days, close them at least 12 hours before you start.
Can I buy a radon test kit at a hardware store?
Yes. Passive test devices are sold in hardware, drug and other stores and by mail or phone, and at some home improvement stores.
How do I get a free radon test kit?
Ask your state radon program or county health department. See free radon test kits by state for the programs that give kits out.
Does the price of a radon test kit include the lab fee?
It depends on the kit. Check the package or the maker's page before you buy; our list shows what the maker says the price covers.
How soon do I need to mail a radon test kit back?
Right away. Reseal the package and send it to the lab named on the package as soon as the test ends.
Do radon test kits expire?
Some do. Finish an alpha track test before the maker's expiry date printed on the package. Check the date before you start.
Should I use two radon test kits?
Two kits help when the result matters, as in a home sale. Two tests at the same time improve precision, and two tests one after the other better represent the seasonal average.
Is a radon test kit or a digital radon detector better?
Neither is better in general. A kit gives a lab-read average for one period; a detector gives a running reading you can watch for months. See radon detectors and monitors.
Can I use a home test kit when buying a house?
Yes. Two passive short-term tests, side by side or one after the other, are accepted, and any real estate test should include steps to prevent or detect interference. Many buyers and sellers use a qualified tester; check your contract and state rules.
What should I do if my radon test kit result is high?
Confirm it with a second test, then plan a fix if the average is high. The results interpreter explains your number, and radon mitigation explains how homes are fixed.
How often should I test my home for radon?
Retest after you renovate or begin using a lower level; even below 4 pCi/L you may want to test again sometime in the future. With a radon system in place, retest at least every two years.
Do I keep windows closed for a long-term radon test kit?
No. Closed-house conditions are for short-term tests, which capture only a few days. During a long-term test, live in the home as you normally do: the point is to measure the radon you breathe over months, with windows, doors and fans used the usual way.
Can I reuse a radon test kit?
Charcoal and alpha track kits are single-use, because the laboratory opens the device to analyze it. An electret detector is not destroyed when it is read, so the device can be used again, but it goes back to a calibrated reader each time. If you want to measure again and again yourself, a radon monitor is the reusable choice; see radon detectors and monitors.
Can I test more than one room with kits?
Yes. One kit on the lowest lived-in level answers the main question, and a second kit on another lived-in floor tells you whether that floor differs. Use kits of the same kind and run them over the same days so the results can be compared.
Questions people ask
Where can I buy a radon test kit?
Yes, a radon test from a qualified laboratory gives a reliable reading when it is used as its instructions say. Most wrong results come from how the test was run, not the device: improper testing may give an inaccurate result, and one short test only captures a few days of a level that changes.
How do you use a radon test kit?
Use a short-term test kit in the lowest lived-in level of your home, or hire a qualified tester: close windows and doors 12 hours before, set the device at least 20 inches off the floor away from drafts, leave it at least 48 hours, then mail it to the lab. A high result gets a follow-up test.
Are home radon test kits accurate?
Yes, a radon test from a qualified laboratory gives a reliable reading when it is used as its instructions say. Most wrong results come from how the test was run, not the device: improper testing may give an inaccurate result, and one short test only captures a few days of a level that changes.
Can I test for radon myself with a kit?
Yes. A do-it-yourself kit from a hardware store, online or by mail is the usual first test, and it takes only a few minutes of your time. Place it in the lowest lived-in level, keep the house closed, leave it for the time the kit says, at least 48 hours, then mail it to the lab.
Where should a radon test kit be placed?
Place a radon test in the lowest lived-in level of the home, in a room used regularly such as a living room or bedroom, not the kitchen or bathroom. Set it at least 20 inches above the floor where it won't be disturbed, away from drafts, high heat, high humidity and exterior walls.
What is a radon test kit?
A radon test kit is a small, low-cost detector you set out in the lowest lived-in level of your home for a set time, then reseal and mail to a lab, which reports the radon level. Short-term kits stay out two days to 90 days, and long-term kits more than 90 days.