If you searched "certified radon testing near me," you're probably trying to figure out whether the person or company that shows up on Google is actually qualified to test your home — and what that certification even guarantees. Here's the straight answer, plus what happens after the test if your numbers come back high.
Who Is Qualified to Do Certified Radon Testing in Wisconsin?
In Wisconsin, radon measurement professionals must be certified through the Wisconsin Department of Health Services (DHS) Radon Program, and many also hold national certification through the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). A legitimate tester should be able to provide their DHS certification number on request — if a company can't produce one, that's a red flag, not a technicality.
Certification matters because it governs how the test is set up, not just who's holding the device. A certified tester follows EPA-published closed-house conditions: windows and exterior doors closed for at least 12 hours before a short-term test begins and kept closed for its full duration (typically 48 hours), with no fans venting outside air in or fireplace use during that window. Skip that protocol and the number on the printout is close to meaningless.
How Does Radon Mitigation Work?
Radon mitigation in Wisconsin almost always uses a method called active soil depressurization (ASD). Here's the actual mechanics of it, since most sites skip past the detail:
- A hole is core-drilled through the basement slab or crawlspace floor, and a suction pit is sometimes excavated beneath it to improve airflow across the soil.
- PVC pipe (typically 3 or 4 inch diameter) is run from that point up through the house — usually through a closet, garage, or exterior wall chase — to a point above the roofline, similar to a plumbing vent stack.
- An inline radon fan, rated for continuous outdoor duty, is installed in that pipe run (often in the attic or outside) and pulls soil gas from beneath the slab before it can enter the living space, exhausting it above the roof edge where it disperses.
- A U-tube manometer is mounted near the pipe, visible from inside the house, so the homeowner can do a 5-second visual check anytime to confirm the fan is still running.
This is different from simply tying into your furnace ductwork — that's a common misconception behind searches for "HVAC radon mitigation." A proper ASD system is a dedicated, separate pipe and fan; it doesn't route through your heating and cooling system, because doing so would recirculate radon-laden air rather than exhausting it outside.
What Is the EPA Radon Action Level?
The U.S. Environmental Protection Agency sets 4.0 picocuries per liter (pCi/L) as the action level at which it recommends mitigation. The EPA also notes there's no fully "safe" level of radon exposure — readings between 2 and 4 pCi/L are still worth discussing with a certified professional, especially in homes with children or non-smokers, since radon is the leading cause of lung cancer among people who have never smoked.
What Should I Expect During a Radon Test?
A short-term test uses either passive charcoal canisters (sent to a lab for analysis) or an electronic continuous radon monitor (CRM), which logs hourly readings and needs to be calibrated on a regular schedule per the manufacturer's spec — ask your tester when their device was last calibrated, since that's a fair and verifiable question. Testing device placement also matters: EPA and DHS guidance calls for the lowest livable level of the home, away from drafts, exterior doors, and windows, and at least 20 inches off the floor.
Seasonality is a common point of confusion. Radon levels do fluctuate with weather and how tightly a house is sealed up, and Wisconsin's cold-weather months (when doors and windows stay shut for long stretches) tend to produce more stable, representative readings. That said, EPA guidance is clear that testing is valid year-round — you don't need to wait for winter to get an accurate result, and waiting means delaying a fix if levels are elevated.
If you're comparing radon risk by area — for instance whether homes in certain Wisconsin counties tend to run higher due to local geology — that's worth reviewing, but it's not a substitute for testing your specific house, since radon levels can vary significantly between neighboring homes on the same street.
What Happens if My Test Comes Back High?
If your certified test result is at or above 4.0 pCi/L, the next step is a confirmation test (either a second short-term test or a long-term test), followed by mitigation system design and installation by a certified mitigator — note that testing and mitigation are sometimes done by the same certified professional, but they're distinct credentials in Wisconsin, so confirm both if one company is doing the full job. After installation, a post-mitigation test should confirm the level has dropped, and most systems bring readings down well below the EPA action level within 24 hours of the fan running continuously.
How does radon mitigation work if I have a crawlspace instead of a basement?
Crawlspaces are usually addressed with a sealed vapor barrier over the exposed soil combined with a suction point run through that barrier to the same type of PVC-and-fan ASD system used in basements — the mechanics are the same, just adapted to the crawlspace geometry.
Can a radon mitigation system be integrated with my HVAC system?
No — a proper active soil depressurization system runs on its own dedicated pipe and dedicated fan, separate from your furnace or air handler ductwork. Tying radon venting into HVAC return or supply lines would risk recirculating soil gas through the house rather than exhausting it outdoors, which defeats the purpose of the system.
What's the difference between active soil depressurization and other mitigation methods?
ASD is the most common and generally most effective method because it actively depressurizes the soil beneath the slab using a fan. Passive systems (pipe only, no fan) rely on natural stack-effect airflow and are less consistently effective, which is why most certified mitigators recommend the active version, especially in homes with elevated initial readings.
This article is educational and general in nature. Radon testing and mitigation requirements, certification standards, and local building rules vary by municipality and county in Wisconsin — always confirm current requirements with your local building inspector and verify a contractor's DHS radon certification directly before hiring.