Testing for radon takes four steps: choose a short-term or long-term test kit, place it on the lowest lived-in level away from drafts and moisture, keep the house closed up for the test period, then seal the kit and send it to the lab. A reading of 4 picocuries per liter (pCi/L) or higher means it is time to call a mitigation professional.
The rest of this guide walks through each of those steps in detail, plus how to read your results, what a test costs, and how often Milwaukee homeowners should retest.
Table of Contents
What Is Radon Testing?
Radon testing measures how much radon gas is present in the air inside a home. Radon is a colorless, odorless gas released as uranium breaks down in soil and rock. It seeps into homes through foundation cracks, sump pits, and gaps around pipes, and it is the only way to find out whether a home has a problem, since you cannot see, smell, or taste it.
A test kit measures radon concentration over a set exposure period, then reports the result in pCi/L. Below 4 pCi/L, a home does not need mitigation, though the EPA notes that levels between 2 and 4 pCi/L are worth reducing where practical. At or above 4 pCi/L, the EPA recommends fixing the home.
Why Milwaukee Homes Need Radon Testing
Milwaukee County sits in EPA Radon Zone 2, the moderate-risk tier that predicts average indoor screening results between 2 and 4 pCi/L countywide. That is a county-level prediction, not a promise about any single house. Homes on either side of the same street can test very differently depending on soil, foundation type, and how tightly the house is sealed.
State-wide, Wisconsin DHS estimates that about 1 in 10 homes test above the EPA action level, and the agency recommends testing every home regardless of its zone. Southeastern Wisconsin, which includes Milwaukee County, is one of the regions the state calls out for closer attention.
Short-Term vs. Long-Term Radon Tests
There are two main test types, and the right one depends on how quickly you need an answer.
| Test Type | Duration | Best For | Typical Turnaround |
| Short-term | 2 to 7 days | Real estate deadlines, quick baseline | Results in 1–2 weeks after mailing |
| Long-term | 90 days or more | Accurate year-round average | Results in 1–2 weeks after mailing |
| Continuous monitor | Ongoing | Post-mitigation verification, high-risk zones | Real-time to next-day readout |
A short-term test is the right call for a real estate closing deadline or a quick baseline check. A long-term test gives a more reliable year-round average, since radon levels shift with the seasons, so it is the better choice if you are not on a deadline.
How to Test for Radon: Step-by-Step
Follow these steps for a reliable result, whether you are running a short-term or long-term test.
- Pick your test type. Choose short-term for a quick read, long-term for a full seasonal average.
- Choose the lowest lived-in level of the home. This is usually a finished basement, a first-floor family room, or a bedroom. Do not test in a kitchen, bathroom, or unfinished crawl space.
- Place the kit correctly. Set it 20 inches or more above the floor, at least 3 feet from an exterior wall, and away from windows, vents, fans, and heat sources.
- Close up the house. Shut exterior doors and windows for at least 12 hours before the test starts, and keep them closed as much as possible for the full test period. Normal entry and exit is fine.
- Leave the kit undisturbed for the full exposure window listed on the package, typically 2 to 7 days for a short-term kit or 90 days or more for a long-term kit.
- Reseal the kit immediately once the test period ends, record the end date and time, and ship it to the lab named on the package the same day if possible.
- Wait for lab results. Most labs return results within one to two weeks of receiving the kit.
These steps follow Wisconsin DHS testing guidance and standard EPA protocol. If you would rather have a certified technician handle placement and pickup, Milwaukee Radon Home’s testing service covers the full process.
Common Placement Mistakes That Ruin a Test
A misplaced kit is the most common reason for a test result that does not match reality. Avoid these mistakes:
- Placing the kit in a kitchen or bathroom, where humidity and cooking fumes skew the reading
- Setting it directly on the floor or right next to a window, door, or air vent
- Opening windows during a cold snap or hot stretch just to “air out” the house mid-test
- Running the test in an unfinished crawl space instead of a lived-in level
- Moving or bumping the device before the exposure period ends
How to Interpret Your Radon Test Results
Once the lab reports your number in pCi/L, here is what it means:
- Below 2 pCi/L: Low risk. No action needed, though the EPA notes no level of radon is completely risk-free.
- 2 to 4 pCi/L: Moderate. The EPA says fixing the home is worth considering, especially if the reading is close to 4.
- 4 pCi/L or higher: The EPA’s action level. A mitigation system is recommended.
For reference, EPA data put the national average indoor radon level at roughly 1.3 pCi/L, with about 0.4 pCi/L typically found outdoors. A single short-term test near the 4 pCi/L line does not always tell the full story since radon fluctuates by season and even by day, so a second test is worth running before making a mitigation decision either way.
DIY Test Kit vs. Professional Radon Testing
A DIY kit works well for a routine check. For a real estate transaction, a new mitigation system verification, or a result close to the action level, a professional test carries more weight, since it follows a documented chain of custody and is harder to challenge in a sale. See our full breakdown of radon test kits and DIY testing devices and our guide to choosing a radon detector for a closer look at both options.
Whichever route you choose, hire or buy from a tester who holds NRPP or NRSB certification. Wisconsin does not run its own state radon contractor license, so these two national bodies are the credential to check.
How Much Does Radon Testing Cost?
A basic short-term DIY kit typically runs $10 to $30, with the lab fee sometimes included. Long-term kits run a bit higher. A professional test with a certified technician costs more but includes placement, pickup, and a documented report.
For a complete cost breakdown by test type and scenario, see how much radon testing costs.
How Often Should You Test for Radon?
- Every 2 years for an established home with no prior high reading
- Before buying or selling a home, regardless of when it was last tested
- After any major renovation that touches the foundation, HVAC system, or lowest level
- Within 24 hours to 30 days after a mitigation system is installed, to confirm it is working
For a closer look at how long a full test cycle takes from placement to results, see our guide to the radon testing process and timeline.
What to Do If Your Radon Level Is High
A confirmed reading at or above 4 pCi/L calls for a mitigation system, most commonly sub-slab depressurization, which vents radon from beneath the foundation before it can enter the home. Properly installed systems typically cut radon levels by 80 to 99 percent. Our Radon Mitigation Systems guide covers how these systems work, what they cost, and what to expect during installation.
If your home also draws from a private well, radon can be present in the water supply too. See Radon System Inspection Services for that separate process.
Frequently Asked Questions
Can I test for radon myself, or do I need a professional?
A DIY kit is fine for a routine check. For a real estate transaction, an insurance claim, or a mitigation system verification, use a certified NRPP or NRSB tester, since a professional chain-of-custody result holds up better in those situations.
Do landlords in Wisconsin have to test for radon?
Wisconsin law requires landlords to disclose any known radon hazard before a tenant signs a lease, but it does not require proactive testing of every rental. If a tenant tests and finds an elevated level, the landlord must be informed, and retaliation against the tenant for reporting it is against the law.
Can weather affect my radon test results?
Yes. Radon levels tend to run higher in winter, when homes are sealed up and the stack effect pulls more soil gas indoors, and lower in mild, breezy weather. Avoid testing during unusually high winds or right after a barometric pressure swing, since both can distort a short-term reading.
How long does it take to get radon test results back?
Most labs turn around results within one to two weeks of receiving a mailed-in kit. A professional continuous monitor can often deliver a same-day or next-day readout instead of waiting on lab mail time.
Is there a blood test for radon exposure?
No. Radon exposure is not measurable through blood, urine, or any other medical test, since the gas passes through the lungs rather than building up in the bloodstream. Air testing inside the home is the only way to know your exposure level.
Conclusion
Testing for radon is a straightforward process: pick a test type, place it correctly, keep the house closed for the exposure window, then read your results against the EPA’s 4 pCi/L action level. Milwaukee’s Zone 2 classification means every home in the metro is worth testing, regardless of the house next door.
Ready for a professional test or have a result you want a second opinion on? Request a free quote or call (414) 455-7279 to talk with a certified Milwaukee Radon Home technician.
