Radon test came back high? Here's what to do next
The EPA recommends fixing a home at 4 pCi/L or higher. Answer three quick questions to see your next step, from a second test to a certified contractor.
What should you do if your radon test is high?
Don't panic, and don't put it off. The EPA recommends fixing your home if one long-term test, or the average of two short-term tests, shows 4 pCi/L or higher. Wisconsin's radon program says to confirm a first high result with a second test, then hire a certified radon contractor if the average stays above 4. Radon levels in most homes can be brought down to 2 pCi/L or below. Not sure what your number means? Try the radon level checker.
Question 1. How many radon tests have you done?
Why we ask: one short-term test isn't the whole picture.
- One test: do a second test, either short-term or long-term. If your first result was 8 pCi/L or higher, Wisconsin's radon program says to do a second short-term test right away.
- Two tests: average the two results. If the average is above 4, plan a fix.
- One long-term test: a result of 4 pCi/L or higher means it's time to plan a fix.
Need a test? See how to test for radon.
Question 2. Have you found a radon contractor?
Why we ask: Wisconsin doesn't require radon contractors to be licensed or certified, so it's up to you to check.
- Not yet: look for a certified mitigation specialist with the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). Wisconsin's radon program suggests getting estimates from at least three companies. Or request a free quote, and we'll look for one certified contractor who serves your area.
- You have one: make sure their certificate is active in the NRPP or NRSB database before you sign.
- Getting estimates: ask each contractor whether they test after installation, what the warranty covers, and whether the system will be labeled with a warning gauge you can see.
Wondering about cost? See radon mitigation cost in Wisconsin.
Question 3. Is your radon system already in?
Why we ask: the job isn't done until a test says it worked.
- Not yet: request a free quote.
- Just installed: test again within 30 days, but no sooner than 24 hours after the system is running with the fan on.
- Installed a while ago: retest at least every two years. Keep the fan running all the time, and check the warning gauge now and then to make sure the system is working.
Ready to get it fixed?
Tell us your ZIP code and your result. We'll look for one NRPP or NRSB certified radon contractor who serves your area, and your request goes to that one contractor, never a list.
Prefer to call? (414) 775-3622. Call or leave a message.
- Certified contractors only (NRPP or NRSB). Free, no obligation.
- Wisconsin Radon Help connects homeowners with certified radon contractors. We don't do the testing or the fix ourselves.
- Sources: US EPA's Consumer's Guide to Radon Reduction and guide to buying a home, and the Wisconsin Department of Health Services radon program. Read November 2026.
Frequently asked questions
Is one high radon test enough?
Wisconsin's radon program says to do a second test when the first comes back at 4 pCi/L or higher, and a second short-term test right away if the first was 8 or higher.
How do I know a radon contractor is certified?
Wisconsin doesn't require certification, so check that the contractor's certificate is active with the NRPP or the NRSB before you hire them.
When should I test again after radon mitigation?
The EPA says within 30 days of installation, but no sooner than 24 hours after the system is running, and then at least every two years.