Rochester Area Radon Data
Local radon levels, by city, county, and census tract.
Median radon test results across our service area, pulled from the Minnesota Department of Health, Radon Testing public dataset (2014–2023). Every number on this page is a real measurement from a real address, averaged with the rest of the tract or county it sits in.
The headline
- 59.5% of tested Dodge County homes are at or above the EPA action level of 4 pCi/L.
- 42.3% of tested Olmsted County homes are at or above 4 pCi/L.
- 62 of 87 Minnesota counties have a county-wide average at or above 4 pCi/L.
- Median radon values across Rochester's 28 census tracts run from 2.2 to 5.3 pCi/L.
How radon levels stack up across the service area
Every city we serve sits in one of four southeast Minnesota counties. Olmsted, Dodge, Fillmore, or Goodhue. Across the 11 cities below, median radon levels span more than 3 pCi/L. The smaller towns south and west of Rochester are not lower than Rochester. In most cases they are higher.
The Rochester median is 3.2 pCi/L, below the EPA action level on average. Mantorville, Spring Valley, Chatfield, Preston, Kasson, Oronoco, Zumbrota, and Stewartville all sit at or above 4. Mantorville comes in at 6.4 pCi/L, the highest in the area.
What changes the city-to-city number
- Sample size. Rochester's number averages across more than 900 tests a year. Mantorville averages 30. Small samples can swing harder when one or two basements with unusual readings show up.
- Ground beneath. Fillmore and Dodge counties sit in karst country. Shallow limestone, sinkholes, caves, and fractures that channel soil gas. Olmsted and Goodhue still sit on limestone, with more glacial overburden on top of it.
- Housing era. Older central blocks in Mantorville, Chatfield, and Preston have foundations that predate modern building practice. Pine Island and Byron are mostly post-2010 builds with engineered slabs.
By county: how often a tested home comes back above 4 pCi/L
The county-level number is the cleanest way to compare areas. It is the share of tested properties whose result lands at or above the EPA action level. None of our four service counties dip below 40%.
Dodge County (Kasson, Mantorville) ranks 20th of 87 Minnesota counties. Fillmore County (Chatfield, Preston, Spring Valley) ranks 31st. Goodhue County (Pine Island, Zumbrota) ranks 41st. Olmsted County (Rochester, Byron, Oronoco, Stewartville) ranks 54th.
All four are above the U.S. national average. Olmsted is the lowest of the four, mostly because the Rochester urban core has newer housing stock and thicker glacial cover than the rural areas around it. The rural townships in Olmsted look more like Dodge and Fillmore than they do like Rochester proper.
Inside Rochester, by census tract
The citywide Rochester average is 3.2 pCi/L. That number hides a lot. Across 28 census tracts, tract-level medians range from 2.2 to 5.3 pCi/L. The highest tract sits at about 2.4 times the lowest.
Over the ten-year window, about 9,320 Rochester properties have been tested, out of roughly 53,000 housing units the tracts cover. That works out to about 17% of Rochester homes with at least one tested result on file. The other 83% are still an open question.
The high-radon tracts cluster along Rochester's south and east sides, where the soil cover over the limestone is shallower and the housing is more mixed in age. The low-radon tracts are in the central and west areas with more newer construction and thicker overburden.
We do not draw a straight line from "your neighborhood is high" to "your house is high." Radon varies house to house even on the same street. The tract numbers are a useful baseline, not a forecast.
Winter is the honest test
Minnesota seasonal radon averages, statewide, are the cleanest argument for testing in the cold months. The winter mean is 26% higher than the summer mean. When your furnace runs, warm air leaves the top of the house and pulls soil gas in through the basement floor. Outside doors and windows stay closed. Both effects push the indoor number up.
The Minnesota Department of Health and Olmsted County Public Health both recommend testing in the cold months for this reason. For a real estate sale, the rules are the same year-round. Closed-house conditions for at least 12 hours before and during the test.
Statewide context
- Zero Minnesota counties have a county-wide radon average below 2 pCi/L. None.
- 25 counties sit between 2 and 4 pCi/L. 62 counties sit at or above 4 pCi/L. That is roughly 71% of the state.
- Minnesota's overall arithmetic mean is 3.9 pCi/L. The U.S. average is closer to 1.3 pCi/L.
- Between 22,000 and 39,000 Minnesota homes are tested for radon each year, with a noticeable lockdown-year bump in 2020.
Rochester is a high-radon city. The smaller towns around it are higher. Most of Minnesota looks the same. The local question is not whether radon is real here. It is what your specific basement is doing about it.
About the numbers
All readings on this page come from the Minnesota Department of Health, Radon Testing public dataset (2014–2023). City rows are at the census-tract level. For most small towns we serve, the city and a single tract are the same place. Rochester spans 28 tracts and is shown both citywide and by tract.
The median is the middle reading across all tests in that location. The geometric mean is a log-scale average and tends to track better when the distribution has a long upper tail, which radon distributions always do. Tests per year is the rolling 10-year average. Housing units is the count the tract is sized against, not the count of tested homes.
A reading from one home is not a forecast for another home next door. Indoor radon depends on slab condition, foundation type, how the home is sealed, and what the rock under the foundation is doing. The right next step for any individual home is its own test.
Find out where your home actually sits.
The data on this page is the picture across thousands of basements. The picture in your basement is its own story, and the first step is a free test.