Radon is the second leading cause of lung cancer in the U.S. — and one of the most fixable problems in your home. This guide explains permits, contractor licensing requirements, and what your pCi/L result actually means, organized by state.
Not sure what your result means or where to begin? Follow this path.
pCi/L explained in plain English — borderline levels, seasonal variation, and when to re-test vs. act immediately.
State-by-state guide to radon mitigation permit requirements — building permits, electrical permits, and contractor licensing.
What NRPP and NRSB certification means, how to verify a contractor before hiring, and questions to ask.
From your test result to a signed-off post-test: every step of the mitigation process explained.
State-by-state DIY rules, technical requirements your install must meet, and when you still need a professional.
Enter your pCi/L result and state → get specific next steps, permit notes, and contractor requirement info.
Enter your test result and state below for personalized guidance.
Permit requirements, contractor licensing rules, and local details — organized by state.
From understanding your test to verifying a contractor's credentials.
pCi/L explained, test types, and what different numbers mean.
Borderline levels, seasonal variation, and the re-test decision.
Every step from diagnosis to post-mitigation sign-off.
How SSD works, when it's used, and what the fan does.
HP, RP, and CF series fans — sizing guide and application chart.
What to expect in the first 24 hours, 48 hours, and 30 days.
Legal status by state, technical requirements, and what can go wrong.
Testing, treatment options, and when water radon matters.
What sellers must disclose and how to prepare for buyer inspections.
When, where, and how to test — plus what a passing result looks like.
Pre-mitigation diagnostics explained — and when you need one.
Mitigation options for crawl space foundations.
One-page homeowner checklist — from understanding your number to post-mitigation sign-off. Print it before calling a contractor.
Download Free PDF →The EPA divides the U.S. into three radon potential zones based on geology, soil permeability, and historic testing data.
Predicted average indoor radon above 4 pCi/L. Testing is urgently recommended. States with the most Zone 1 counties: Pennsylvania (all counties), Iowa, Illinois, Minnesota, Colorado, Ohio.
Predicted average 2–4 pCi/L. Testing still recommended — individual homes in Zone 2 frequently test above 4 pCi/L. Zone is a guideline, not a guarantee of safety.
Predicted average below 2 pCi/L. Testing still advisable, especially for basements or below-grade living spaces. Zone 3 homes can test high due to local geology variations.
⚠️ EPA zones are predictions, not guarantees. The only way to know your home's radon level is to test it. Zone 3 homes can and do test above 4 pCi/L.
View full EPA zone map explanation and county list →