Radon testing at home is simple, and it is the only way to know your level. The U.S. Environmental Protection Agency (EPA) says plainly that "all homes should be tested for radon" and that you can't see or smell it. You start with a short-term test kit on the lowest lived-in level of the house, with windows and exterior doors kept closed. If the result is high, you confirm it with a follow-up test. EPA recommends fixing a home at 4 picocuries per liter (pCi/L) or above, and suggests considering a fix between 2 and 4 pCi/L.
That is the short version. The rest of this page walks through what the gas is, the two kinds of test, where the kit goes, how to read the number you get back, and who to call if the number says act. It sticks to what EPA and a state health department say. It does not estimate your personal health risk, because that is a conversation for a doctor, not a home maintenance blog.
What radon is, in plain terms
Radon is a naturally occurring radioactive gas. It comes up out of the ground and can collect inside a building, especially in the lower levels. On its main radon page, EPA calls radon "the second leading cause of lung cancer" and makes the point that matters most for a homeowner: "Testing is the only way to know your level of exposure."
Two things follow from that.
- You cannot judge it by the house. New or old, basement or slab, a neighbor's result does not tell you yours. EPA's position that every home should be tested is exactly because you cannot predict one house from another.
- You cannot sense it. There is no smell, no stain, no symptom in the house itself to tip you off. A test is the whole method.
EPA's Health Risk of Radon page (read on 2026-09-27) gives two reference points that help put your own result in context: the average indoor radon level is listed at "1.3 pCi/L (50 Bq/m3)" and the average outdoor level at "0.4 pCi/L (15 Bq/m3)." Those are averages, not safe lines. They are useful mainly so a result of, say, 6 pCi/L does not look like a small number.
Radon testing at home: short-term vs long-term tests
There are two broad kinds of test, and they answer slightly different questions.
| Short-term test | Long-term test | |
|---|---|---|
| What it tells you | A snapshot of radon during the test window | A better estimate of the year-round average |
| How long it stays in place | The Minnesota Department of Health describes 2 to 7 days | At least 90 days, per the same page |
| Best used for | The first screening test | Deciding whether to fix, especially for middling results |
| Weakness | One short window can read higher or lower than your average | Slower to get an answer |
The Minnesota Department of Health's radon test results page (read on 2026-09-27) recommends a short-term test as the initial screening and a long-term test when you want the better estimate of your annual average. Other state programs describe the windows a little differently, and device instructions vary, so the kit's own directions come first.
A third option, a continuous radon monitor, records radon over time and is often used when a home is being bought or sold. These are usually run by a radon measurement professional rather than a homeowner.
Where to get a test kit
EPA's page on finding a radon test kit or professional lists three routes: discounted kits sold online through the National Radon Program Services at Kansas State University, kits sold "online or in home improvement stores," and your state radon program, noting that "some states also offer free or discounted test kits to the public." It is worth checking the state program first for that reason alone.
How to set up the test so the number means something
A careless setup can undermine a perfectly good kit. The Minnesota Department of Health gives specific placement guidance, and it lines up with what most kit instructions say:
- Lowest lived-in level. Test the lowest level of the home you actually use, such as a finished basement family room, not a crawlspace nobody enters.
- Height. The kit should sit "at least 20 inches above the floor, preferably at your 'breathing level.'"
- Distance from walls and windows. Minnesota's guidance is "1 foot from exterior walls, 3 feet from exterior windows, and away from drafts."
- Rooms to avoid. Kitchens, bathrooms, laundry rooms, and spots near fireplaces and furnaces.
- Closed-house conditions. For tests shorter than three months, Minnesota says to keep "all windows and exterior doors closed, except for normal entry and exit," and to run heating or cooling as you normally would.
A few practical notes on top of that:
- Write the start date and time on the kit or the lab form. Most labs ask for it.
- Do not move the kit mid-test.
- Mail it back as soon as the test ends, within whatever window the kit instructions give.
- If you are in the middle of a big renovation that opens up the foundation, it makes sense to test after the work rather than during it.
If you keep a yearly routine for the house, add a line for radon to your home maintenance checklist so a retest does not quietly slip by for a decade.
What the numbers mean
Your result comes back in picocuries per liter (pCi/L) in the U.S., or becquerels per cubic meter (Bq/m3) in many other countries. Here is how EPA and the Minnesota Department of Health frame the ranges.
| Result | What the sources say |
|---|---|
| 4 pCi/L (150 Bq/m3) or higher | EPA recommends fixing the home. Its health-risk page stresses the need "to remedy the problem as soon as possible" at this level. |
| 2 to 4 pCi/L (75 to 150 Bq/m3) | EPA says to "consider fixing between 2 and 4 pCi/L." |
| Below 2 pCi/L | Minnesota recommends retesting every 2 to 5 years. |
Note what the table does not say. It does not say anything below 4 is safe. EPA's own wording for the 2 to 4 band is "consider fixing," and that is a deliberate choice. The action level is a line for action, not a line between safe and unsafe.
What to do with a first result
Minnesota's page lays out the next step based on the first test, and it is one of the clearest decision paths published by a state:
- 0 to 1.9 pCi/L: retest in 2 to 5 years.
- 2 to 7.9 pCi/L: do a long-term follow-up test.
- 8 pCi/L or higher: do a short-term follow-up test, so you get confirmation quickly.
Then the follow-up result drives the decision: 4 pCi/L or more, mitigation is recommended; 2 to 3.9, consider mitigation; under 2, retest every 2 to 5 years.
The logic is worth understanding. A middling first number gets a long-term follow-up because the long test gives the better estimate of your average. A very high first number gets a quick short-term follow-up because waiting three months to confirm a high reading is three months spent at that level.
If the number says fix it: who does the work
Radon reduction (usually called mitigation) is a job for a qualified radon mitigation professional. This page does not describe how to install a system, and that is on purpose: a system has to be designed for the specific house, and the work can involve the foundation, venting and a fan, which brings in electrical connections. Anything electrical beyond plugging something in belongs to a licensed electrician.
How professionals are credentialed depends on where you live. EPA's page on finding a professional says the agency points to either "an existing state-run process established under a state's regulatory requirements for credentialing radon service providers" or one of two national programs: the National Radon Proficiency Program (NRPP) and the National Radon Safety Board (NRSB). EPA also advises contacting "your state radon program for help in finding qualified professionals in your state."
Whether a mitigation system needs a permit is set by your city, county or state, not by any national rule. The honest way to find out is to call your local building department and ask, and to ask the mitigation contractor what they plan to pull for your address. A contractor who is vague about local permits is worth a second opinion.
After any mitigation work, retest. Ask the installer what follow-up test they recommend, and check what your state radon program expects.
Radon and moving into a home
Radon often comes up for the first time during a home purchase. If you just moved in and no test was done, radon is a good candidate for the first month, alongside the other must-find items on our first 30 days in a house checklist. Your state radon program can explain local practices around testing and disclosure during a sale, which vary from place to place.
What this page will not tell you
In keeping with how we write about anything that touches health:
- No personal risk estimate. EPA's own health-risk material separates smokers and non-smokers, which shows how much the answer depends on the person. Only a clinician can talk about what exposure means for you or your family.
- No symptom checklist. If you have health concerns about past radon exposure, talk to your doctor.
- No DIY mitigation steps. The test is homeowner territory. The fix is professional territory.
Frequently asked questions
How long does a radon test take?
It depends on the kind. The Minnesota Department of Health describes short-term tests as running 2 to 7 days and long-term tests as a minimum of 90 days. Your kit's instructions give the exact window for that device.
What is a safe radon level?
EPA does not describe any level as safe. It recommends fixing a home at 4 pCi/L or higher and suggests considering a fix between 2 and 4 pCi/L. For context, EPA lists the average indoor level at 1.3 pCi/L.
Where should I put a radon test kit?
On the lowest lived-in level of the home, at least 20 inches above the floor, away from exterior walls, windows and drafts, and not in a kitchen, bathroom or laundry room, per the Minnesota Department of Health's guidance.
Should I retest if my first result was low?
Yes, periodically. Minnesota recommends retesting every 2 to 5 years when results are under 2 pCi/L. Retesting also makes sense after major work on the foundation.
Do I need a permit to install a radon mitigation system?
That depends on your city, county and state, so there is no single answer. Call your local building department and ask, and ask any mitigation contractor what permits they plan to pull for your address.
