Published: 2026-03-06 | Home Inspector New Ulm
Radon Levels in Southern Minnesota: What Homeowners Must Know
If you own or are buying a home in southern Minnesota, radon should be on your radar. The EPA classifies the entire region, including Brown County (New Ulm), Blue Earth County (Mankato), and Nicollet County (St. Peter), as Zone 1, the highest risk category for radon exposure.
What is Radon and Why Is It Dangerous?
Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock. It is colorless, odorless, and tasteless, which means you cannot detect it without testing. Radon enters homes through cracks in foundations, gaps around pipes, sump pits, and any opening where the home contacts the ground.
The health risk is serious: radon is the second leading cause of lung cancer in the United States, responsible for an estimated 21,000 deaths per year. The risk increases with the concentration level and duration of exposure.
Radon in Brown County and Surrounding Areas
According to the Minnesota Department of Health, approximately 2 in 5 Minnesota homes test above the EPA action level of 4.0 pCi/L. In some southern Minnesota counties, the rate is even higher.
The geology of our region contributes to elevated radon levels. The glacial till and limestone bedrock beneath Brown, Blue Earth, Nicollet, Redwood, and Watonwan counties contain higher concentrations of uranium-bearing minerals compared to other parts of the state.
Why Radon Levels Vary Between Homes
Two homes on the same street can have dramatically different radon levels. Factors include:
- Foundation type - Full basements tend to have higher levels than slab-on-grade
- Foundation condition - More cracks and gaps mean more radon entry points
- Soil type - Sandy and gravelly soils allow radon to move more freely
- Home ventilation - Tighter, more energy-efficient homes can trap radon inside
- Negative pressure - Furnaces, exhaust fans, and dryers create negative pressure that draws radon in
- Season - Radon levels are typically higher in winter when homes are sealed up
When Should You Test for Radon?
- Before buying any home - This is the single most important time to test
- If you have never tested - Every home in southern Minnesota should be tested regardless of age or type
- Every 2 years - The EPA recommends retesting periodically
- After major renovations - Foundation work or HVAC changes can alter radon entry
- After installing mitigation - Verify the system is working properly
Understanding Radon Test Results
| Level (pCi/L) | Risk | Action |
|---|---|---|
| Below 2.0 | Low | No action needed. Retest every 2 years |
| 2.0 - 3.9 | Moderate | Consider mitigation. Retest in 1 year |
| 4.0 - 7.9 | Elevated | EPA recommends mitigation |
| 8.0+ | High | Mitigation strongly recommended |
Radon Mitigation Works
If your test results are above 4.0 pCi/L, a radon mitigation system can reduce levels by up to 99%. The most common system is a sub-slab depressurization system, which involves:
- A small hole drilled through the basement floor slab
- A PVC pipe routed from beneath the slab to above the roofline
- A quiet, continuously running fan that draws radon from under the slab and exhausts it above the roof
Typical installation cost: $800 to $1,500. Operating cost: about $5-10 per month in electricity. This is one of the most cost-effective health protections you can invest in.
Professional Radon Testing in New Ulm & Mankato
We use calibrated continuous radon monitors (CRMs) that provide hour-by-hour readings over a 48-hour minimum test period. This provides more accurate and tamper-evident results compared to passive charcoal test kits.
Schedule your radon test in New Ulm, Mankato, St. Peter, Sleepy Eye, Fairmont, Waseca, or anywhere in southern Minnesota. Call (507) 205-7067.
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