Radon testing measures how much radioactive radon gas is in your home’s air, reported in picocuries per liter (pCi/L). If your result comes back at or above the EPA’s action level of 4 pCi/L, the next step is radon mitigation most often a sub-slab depressurization system installed by an NRPP- or NRSB-certified technician. Testing takes anywhere from 48 hours to a year depending on which test you use, and a mitigation install is usually a one-day job.
- Under 2 pCi/L: no action needed, retest every two years
- 2 to 3.9 pCi/L: consider fixing, and retest to confirm the trend
- 4 pCi/L or higher: EPA recommends installing a mitigation system
- A correctly installed mitigation system typically brings levels below 2 pCi/L
Table of Contents
What a Radon Test Measures
Radon is a colourless, odourless, radioactive gas produced when uranium in soil and rock breaks down. It moves up through the ground and into homes through foundation cracks, sump pits, and gaps around pipes and drains. Because it has no smell, colour, or taste, a test is the only way to know whether it’s building up inside a house.
The Environmental Protection Agency (EPA) and CDC list radon as the second leading cause of lung cancer in the United States after smoking, and the leading cause among people who have never smoked. EPA and CDC estimate radon exposure is responsible for roughly 21,000 lung cancer deaths every year.
There is no safe level of radon, but the EPA sets 4 pCi/L as the action level, the point at which it recommends fixing a home. Levels between 2 and 4 pCi/L still carry some risk and are worth addressing when practical.
How a Radon Test Works
A Radon System Inspection works by placing a detector in the lowest level of the home that’s regularly used usually a basement or first floor for a set period under closed-house conditions, meaning windows and exterior doors stay shut except for normal entry and exit. Depending on the device, the kit is then either mailed to a lab for analysis or read directly from a digital monitor.
Placement and timing affect accuracy more than people expect. A test run during a mild, breezy week with windows cracked open will read lower than the home’s true winter average, which is why the Wisconsin DHS recommends closed-house conditions and notes that levels typically run higher during cold months, when homes are sealed up and heating systems are running. For a full walkthrough of setup, timing, and what to expect day by day, see how long the radon testing process takes in a Milwaukee home.
Short-Term, Long-Term, and Professional Tests Compared
There are three practical ways to test a home, and they answer slightly different questions.
| Test Type | Duration | Typical Cost | Best For |
| Short-term kit (charcoal or alpha-track) | 2 to 7 days | $10–$30 (WI DHS-listed retail range) | A fast first read on a home that hasn’t been tested |
| Long-term test | 90 days to 1 year | $20–$70 (WI DHS-listed retail range) | A seasonal average, the most representative picture of year-round exposure |
| Professional / continuous monitor | 48 hours or more | National aggregators list $150–$700 | Real estate transactions and any result that needs a calibrated, defensible reading |
For a closer look at which kit to buy and how to use one correctly, see should I get a radon test.
What Your Radon Test Results Mean
| Result | What It Means |
| Below 2 pCi/L | Low risk. Retest every two years or after major renovations, per Wisconsin DHS guidance. |
| 2 to 3.9 pCi/L | Elevated but below the action level. EPA notes some risk remains at this range; many homeowners choose to fix. Retest to confirm before deciding. |
| 4 pCi/L or higher | At or above the EPA action level. A second test is recommended to confirm, then mitigation. |
Why Testing Matters for Milwaukee Homes Specifically
Wisconsin’s Department of Health Services estimates that roughly one in ten homes statewide has an elevated radon level. Milwaukee’s housing stock adds to the case for testing rather than assuming: a large share of the metro’s homes have full basements, and many were built before radon-resistant construction techniques were common.
Milwaukee County is served by the Southeast Wisconsin Radon Information Center, one of 17 regional centers the state runs to make low-cost test kits available locally, and the City of Milwaukee Health Department notes that the MKE Fresh Air Collective offers free radon testing in some city zip codes. Both are useful pointers for a reader who wants a low-cost first test before calling a contractor.
When a Test Result Means It’s Time to Mitigate
A single high reading is worth confirming before committing to a system. EPA guidance is to follow an initial result at or above 4 pCi/L with a second test, either a short-term retest for a faster answer or a long-term test for a more representative one, then proceed to mitigation once the elevated level is confirmed.
How Radon Mitigation Systems Actually Work
The most common fix, used in the large majority of homes with a basement or slab foundation, is active sub-slab depressurization (ASD). The process, per EPA’s Consumer’s Guide to Radon Reduction:
- A technician cores a suction point through the basement floor slab and creates a small pit in the material below it.
- A PVC pipe runs from that point up through the house, or along an exterior wall, to a discharge point above the roofline.
- An inline fan, mounted in the pipe run outside the living space, runs continuously to pull soil gas out from under the slab and vent it above the roof, where it dilutes into outdoor air.
- Cracks and openings in the slab get sealed so the system can hold negative pressure and radon can’t find another way in.
Properly designed sub-slab suction systems reduce radon by 50 to 99 percent, and EPA notes that radon reduction systems overall can bring levels down by up to 99 percent. Homes with hollow block-wall foundations or a sump pit sometimes use block-wall suction or sump-hole suction instead, which work on the same negative-pressure principle. For the full range of system types and how a technician decides between them, see how radon mitigation systems work.
What Does Radon Testing and Mitigation Cost?
EPA’s own Consumer’s Guide puts the typical cost to fix a home at $500 to $2,500, depending on home size, foundation type, and which reduction method is needed. National aggregator data from Angi and HomeAdvisor puts current 2026 averages narrower, around $1,000 to $1,050 for a standard sub-slab system, with a typical range of roughly $787 to $1,281.
For a full cost breakdown, including what changes the price on a specific home, see how much does radon testing cost.
What Should You Look for in a Radon Contractor?
Wisconsin does not require a state license for radon testing or mitigation professionals. The Wisconsin DHS instead recommends hiring someone nationally certified through the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB), both of which follow ANSI-accredited AARST standards for measurement and mitigation. Before hiring:
- Confirm current NRPP or NRSB certification, not just general contracting experience
- Ask what system design they’d use for your specific foundation type and why
- Get a written scope and price before work starts
- Ask whether a post-installation test is included to confirm the system is working
For a step-by-step vetting checklist, see how to hire a certified radon mitigation contractor in Milwaukee.
Maintaining a System After It’s Installed
- Check the system’s manometer or warning device periodically to confirm the fan is still running it should never be switched off
- Retest every two years, per Wisconsin DHS guidance, or sooner after any foundation work, renovation, or if the warning device signals a problem
- Fans typically last five years or more before needing replacement
FAQs
Can I test for radon myself, or do I need a professional?
A DIY short-term or long-term kit is a reliable, inexpensive first step for most homeowners, and Wisconsin’s Radon Information Centers sell them at cost. Real estate transactions and any result you plan to act on with mitigation typically call for a calibrated professional or continuous monitor instead, since consumer digital monitors aren’t approved by NRPP or NRSB for those decisions.
Is it normal for radon levels to change between tests?
Yes. Radon fluctuates with weather, season, and how tightly a house is closed up. A single short-term test is a snapshot, not a guarantee, which is why a confirmatory second test is standard practice before committing to mitigation.
Will a mitigation system change my energy bills?
An active sub-slab depressurization system runs a small continuous fan, which adds a modest amount to electricity use, but it doesn’t meaningfully change home heating or cooling costs the way opening windows for ventilation-based reduction would.
What happens if I skip mitigation after a high result?
The radon level doesn’t resolve on its own. Continued exposure at or above 4 pCi/L keeps the elevated lung cancer risk EPA and CDC describe, and the risk compounds for smokers. Retesting without addressing the source doesn’t lower the reading.
Do I need to retest after moving into a home that already has a mitigation system?
Yes. Confirm the system is still running and get a fresh test rather than relying on the previous owner’s paperwork. Fans and seals do wear out, and a system that worked at installation can drift over years.
Conclusion
A test is the only way to know where your home actually stands. If you haven’t tested yet, or you have a result you’re not sure how to act on, schedule a radon inspection with Milwaukee Radon Mitigation and get a clear, calibrated read plus next steps if mitigation is needed.
For the full picture of how testing fits into the broader radon story, start with the pillar guide: Radon Testing: How It Works, Cost & Where to Get Tested.
If you feel the urge to act now, call 414-455-7279 and ask about a free evaluation and install strategy. The phone price is a small price on a safety that stays in place with clearing steps and ongoing patience from radon testing and mitigation.
