Radon Testing in Minnesota: Complete Homeowner Guide (2026)
Minnesota Has One of the Highest Radon Rates in the Country
About 40% of homes tested in Minnesota show radon levels at or above 4 pCi/L, the EPA action level. That is roughly 2 in 5 homes. The national average is about 1 in 15. If you own a home in Minnesota and have never tested for radon, the statistical odds are not in your favor.
Radon is a colorless, odorless radioactive gas. It forms as uranium in rock and soil slowly breaks down. It seeps upward through the ground, enters homes through cracks in foundations, gaps around pipes, and through porous concrete, and accumulates in the air you breathe. Long-term exposure is the leading cause of lung cancer in non-smokers in the United States, responsible for about 21,000 deaths annually. The only way to know your exposure level is to test.
Minnesota is classified as EPA Zone 1, the highest-risk category. The Minnesota Department of Health (MDH) radon program is one of the strongest in the country and provides detailed county-level and zip-code-level data on test results across the state.
Why Minnesota Has Such High Radon Levels
The geology beneath Minnesota is the reason. The Canadian Shield, one of the oldest rock formations on Earth, underlies much of the state. Canadian Shield granite contains some of the highest natural concentrations of uranium found anywhere in North America. As that uranium decays over billions of years, it produces radium, which produces radon gas.
During the last ice age, glaciers ground across the Canadian Shield and carried uranium-rich rock fragments south, depositing them across Minnesota as glacial till. That till now underlies the Twin Cities metro, the agricultural plains of southern Minnesota, and broad stretches of the state. The Twin Cities literally sit on a layer of crushed uranium-bearing granite transported there by glaciers.
In the northeastern part of the state, the bedrock rises closer to the surface. Duluth, the Iron Range, and much of St. Louis County sit directly on Superior granite, an ancient formation with very high uranium content. Homes in this region often show some of the highest radon readings in the state.
Across Minnesota, the combination of uranium-rich bedrock, widespread glacial till, cold winters that seal homes tightly, and basement-heavy residential construction creates ideal conditions for radon accumulation.
Where Radon Risk Is Highest in Minnesota
Rochester and Olmsted County
Rochester consistently records some of the highest average radon readings in Minnesota. MDH data shows Olmsted County as one of the highest-risk counties in the state. If you are buying or own a home in Rochester, radon testing is not optional; it is expected. Most Rochester real estate agents and home inspectors treat radon testing as a standard step in every transaction.
The Twin Cities Metro
Hennepin, Ramsey, Anoka, Dakota, Scott, Carver, and Washington counties all sit on glacial till derived from Canadian Shield granite. Radon is a known, understood risk in the Twin Cities market. Radon testing is standard in metro-area real estate transactions, and disclosure of known test results is required by Minnesota law. A home with an untested basement is a negotiating point in Twin Cities transactions.
Duluth and the Iron Range
St. Louis County encompasses Duluth and much of the Iron Range, including Hibbing, Virginia, and Eveleth. The bedrock here is Superior granite, close to the surface and exceptionally high in uranium. Many homes in this region are older, with stone or poured-concrete foundations that offer more entry points for soil gas. Radon levels in this area are among the highest in the state. Test any home in this region before spending extended time in the lowest level.
Northern Minnesota Lake Cabins
The lakes region of northern Minnesota, including areas around Brainerd, Walker, Ely, and Grand Marais, sits on Canadian Shield granite bedrock. Many cabins in this region have basements or crawl spaces in direct contact with granite or granite-rich soils. Cabins are often closed up for extended periods, which allows radon to accumulate. If you spend significant time in a northern Minnesota cabin, test it before assuming it is safe. The geology creates high risk, and many cabin owners have never thought to check.
When to Test in Minnesota
Test During Heating Season
MDH recommends testing from October through April. This is the period when homes are sealed most tightly against Minnesota's extreme winter cold, which regularly brings temperatures of -20°F and wind chills of -40°F or lower. During these months, the stack effect is strongest: warm air rises and escapes through the upper structure, creating negative pressure at the foundation level that draws soil gas into the home.
Testing during summer, when windows are open and the house breathes freely, can significantly undercount your actual winter exposure. A summer test may read 30 to 50 percent lower than the same home during heating season. If you want to know your real exposure, test when the home is sealed and the heat is running.
Test When Buying or Selling
Minnesota law requires sellers to disclose known radon test results. In the Twin Cities metro and in Rochester, radon testing is a standard part of the inspection contingency period. Buyers routinely request a professional radon test as part of the home inspection. A result above 4 pCi/L gives buyers grounds to negotiate for mitigation, a price reduction, or both under standard purchase agreement terms.
For a real estate transaction, use a professional tester with a continuous radon monitor (CRM). Results are ready within 24 to 48 hours of test completion, which fits standard 10-day inspection windows.
Other Times to Test
- If you have never tested your current home
- After finishing or remodeling a basement
- After any major foundation work
- Every two years as a routine check, even if previous results were low
- Before spending extended time in a cabin or seasonal property
Types of Radon Tests
Short-Term Tests: Charcoal Canisters and CRMs (2 to 7 Days)
Short-term tests give a snapshot of radon levels over 2 to 7 days. Two types are common:
- Continuous radon monitors (CRMs): Electronic devices used by professional testers. They record radon concentrations hour by hour, are tamper-evident, and provide a detailed data log. Standard for real estate transactions in Minnesota. Results available within 24 to 48 hours.
- Charcoal canisters: Passive devices available as DIY kits at hardware stores or through the mail. Suitable for personal screening. Not accepted for real estate transactions unless placed by a certified professional under proper conditions.
If a short-term test returns a result between 4 and 8 pCi/L, EPA guidelines recommend a second confirmatory test before committing to mitigation, unless the test was conducted by a professional under strict closed-house conditions.
Long-Term Tests: Alpha Track Detectors (90 Days to 1 Year)
MDH recommends long-term alpha track testing for homeowners who want the most accurate picture of their annual radon exposure. This is especially relevant in Minnesota, where the gap between summer and winter readings can be large due to the state's extreme climate swings. A long-term test captures the full seasonal range and gives a more reliable annual average than any short-term test can.
Alpha track kits cost $20 to $50 for DIY use. Place them in the lowest livable level of the home for 90 days to one year. Long-term tests are not suitable for real estate transactions but are ideal for confirming whether mitigation is needed after an elevated short-term result, or for verifying that a mitigation system is performing across a full heating season.
Post-Mitigation Tests
After a mitigation system is installed, a follow-up test confirms that it is working. Most Minnesota contractors include a post-mitigation test as part of the installation. MDH recommends testing again after installation and then annually. The post-mitigation test is not optional; it is the proof that the system reduced your levels below 4 pCi/L.
Cost of Radon Testing in Minnesota
| Test Type | Cost Range | Best For |
|---|---|---|
| Professional short-term (CRM) | $100 to $300 | Real estate transactions, initial screening |
| DIY charcoal canister | $15 to $40 | Personal screening, routine re-testing |
| DIY alpha track (long-term) | $20 to $50 | Annual average, seasonal accuracy (MDH-recommended) |
| County public health programs | Free or low cost | Personal screening, awareness testing |
MDH offers free or low-cost radon test kits through county public health departments. Availability varies by county and program year. Check with your county public health office to see what is currently available in your area. These kits are suitable for personal screening but typically not for real estate use.
Professional testing costs vary across the state. The Twin Cities metro has enough certified testers to keep prices competitive toward the lower end of the $100 to $300 range. Rochester has strong coverage given the high local awareness. In rural areas and northern Minnesota, travel fees may apply, pushing costs toward or above $300.
Minnesota's MDH Radon Program
The MDH radon program is among the best state programs in the country. MDH maintains a detailed interactive map of radon test results by zip code and county, which you can use to see how your neighborhood compares. The program also publishes guidance on testing protocols, maintains a registry of certified radon professionals, and offers educational resources specifically tailored to Minnesota's geology and climate.
MDH recommends long-term alpha track testing over short-term testing for homeowners (outside of real estate transactions) because Minnesota's extreme seasonal variation means short-term tests can miss the true annual average. This recommendation reflects the state's specific climate reality: a test run in July in a Minneapolis home may read very differently from the same home tested in January.
Minnesota requires both MDH registration and national certification (through NRPP or NRSB) for all radon professionals operating in the state. This dual requirement is designed to ensure that professionals serving Minnesota homeowners meet both national standards and state-specific requirements.
How to Read Your Results
| Result (pCi/L) | Risk Category | Recommended Action |
|---|---|---|
| Below 2 | Low | Re-test in 2 years. |
| 2 to 3.9 | Moderate | Consider a long-term test to confirm. Mitigation worthwhile. |
| 4 to 7.9 | High (EPA action level) | Mitigate. Very common in Minnesota homes. |
| 8 to 19.9 | Very High | Mitigate promptly. Comparable to smoking about half a pack of cigarettes daily. |
| 20 or above | Extremely High | Mitigate as soon as possible. Found in some Minnesota homes, especially in St. Louis County and Olmsted County. |
The U.S. average indoor radon level is about 1.3 pCi/L. Minnesota's average is significantly higher. Results between 4 and 10 pCi/L are common on first screening in Minnesota. Results above 20 pCi/L occur regularly, particularly in the Iron Range and Rochester. A properly installed sub-slab depressurization system can reduce levels by 80 to 99 percent.
The WHO recommends action at 2.7 pCi/L, which is lower than the EPA's 4 pCi/L threshold. Given Minnesota's geology, getting below 2 pCi/L after mitigation is a realistic and achievable goal.
Find a Certified Radon Tester in Minnesota
Ready to schedule a test? Find a certified radon tester in Minnesota in our directory of MDH-registered professionals. Whether you are in Minneapolis, Rochester, Duluth, or a northern lake community, you can find someone serving your area.
Frequently Asked Questions
How much does a radon test cost in Minnesota?
Professional radon testing in Minnesota costs $100 to $300. In the Twin Cities metro and Rochester, pricing is competitive toward the lower end. In rural and northern Minnesota, travel fees can push costs higher. MDH also offers free or low-cost test kits through county public health departments; check with your county office for current availability. DIY charcoal canister kits cost $15 to $40 at hardware stores.
When is the best time to test for radon in Minnesota?
Test between October and April during the heating season. Minnesota's extreme winters seal homes tightly for months, which drives radon accumulation and gives you the most accurate picture of your real exposure. Summer testing may read 30 to 50 percent lower than heating-season testing in the same home. MDH recommends long-term alpha track tests placed during heating season for the most reliable annual average.
Why does Minnesota have so much radon?
The Canadian Shield, one of Earth's oldest granite formations with very high natural uranium content, underlies Minnesota. Glaciers ground across that formation and deposited uranium-rich rock fragments across the state as glacial till. The Twin Cities sit on this glacial layer. In northeastern Minnesota, including Duluth and the Iron Range, Superior granite bedrock is close to the surface. Cold winters seal homes tightly, compounding the risk.
Do I need a radon test when buying a home in Minnesota?
Yes. Minnesota law requires sellers to disclose known radon test results. In the Twin Cities metro and Rochester, professional radon testing is a standard part of every home inspection contingency. A result above 4 pCi/L gives buyers grounds to negotiate for mitigation or a price reduction. Use a certified professional with a continuous radon monitor (CRM) for any real estate transaction.
Should I test a northern Minnesota lake cabin for radon?
Yes. Northern Minnesota sits on Canadian Shield granite, which creates high radon potential. Cabins with basements or crawl spaces in contact with granite soils are especially at risk. Cabins closed up for extended periods allow radon to accumulate. Test during a period of normal occupancy with the heating system running. Many cabin owners have never tested and have no idea what their exposure levels are.