Radon Risk by ZIP Code and Area: What Maps Can (and Can’t) Tell You
Updated September 26, 2026
Data accessed: EPA Map of Radon Zones and related EPA state zone pages reviewed for this refresh on September 26, 2026 (CT).
What changed: Clarified that area/ZIP context is not a home test; removed implication of a proprietary ZIP “database” of indoor averages (none is documented on the live page); prioritized EPA zone maps, state programs, and clear next steps; added a visible FAQ block.
Start here (read this first)
A ZIP code, county average, or color on a map does not tell you the radon level inside your house.
Two homes on the same street can differ dramatically because of foundation type, soil pathways, HVAC, weather, and how the house is lived in. Use this page to contextualize regional potential, find official zone maps and state contacts, and take the only reliable next step: test the air in your home.
If you only remember one line from EPA’s own zone-map guidance: the Map of Radon Zones is for targeting resources and building-code efforts—not for deciding whether a specific home should be tested. EPA recommends testing all homes below the third floor (and more broadly encourages testing).
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Key takeaways
- Radon is colorless, odorless, and radioactive; elevated indoor levels raise lung-cancer risk (EPA/CDC consumer messaging).
- Maps and ZIP summaries ≠ indoor measurements.
- EPA zones (1 / 2 / 3) describe predicted average indoor potential by county, not your basement reading.
- High homes appear in “low” zones; low homes appear in “high” zones.
- Action benchmarks people use from EPA consumer guidance: fix at/above 4 pCi/L; consider action 2–4 pCi/L.
- Next steps: test → interpret → mitigate with credentialed help if elevated → retest.
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What radon is (short version)
Radon forms naturally from uranium decay in soil and rock. It can move through foundation cracks, gaps around pipes, sumps, and crawlspaces and build up indoors—especially in lower levels with limited ventilation. You cannot see or smell it; you measure it.
Public-health agencies link radon to lung cancer risk, including among people who never smoked. Exact risk depends on concentration and time spent indoors; the practical homeowner response is measurement and, if needed, mitigation—not guessing from a map.
For fundamentals, see: What is radon? · Radon facts · Where does radon come from?
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Does a ZIP code show “your” radon level?
No. At best, ZIP- or county-oriented tools show regional summary statistics or zone categories built from historical tests, geology, and models. They answer: “Is this *area* often associated with higher indoor radon?” They do not answer: “What is the picocurie reading in *my* living room?”
Honesty about datasets on this site
As of this refresh, the published Radon.org page at this URL discusses ZIP-oriented risk in prose and points readers to state programs and general online tools. We could not identify a clearly named, cited, licensed ZIP-level indoor-radon average dataset powering an on-page lookup tool in the live HTML. Older marketing copy that promised an “updated database” of ZIP levels was overstated relative to what the page actually delivers.
Until Radon.org documents a specific data provider, license, geography, and refresh date for any ZIP calculator:
- We will not invent ZIP averages (e.g., “your ZIP is 3.47 pCi/L”).
- We will prioritize EPA Map of Radon Zones, state radon program maps/tables, and test-your-home CTAs.
- Our related search by state utility should be treated as a helper—not proof of parcel-level certainty.
If you are evaluating a third-party “radon by ZIP” website, look for: named source, sample size, date range, whether values are predicted vs measured, and a clear limitation statement.
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EPA Map of Radon Zones (primary official reference)
Primary sources (bookmark these):
What the zones mean (plain language)
EPA assigns counties (not individual houses) to zones based on predicted average indoor radon potential:
| Zone | Plain-language meaning | What it does *not* mean |
|---|---|---|
| Zone 1 | Highest predicted potential (predicted average indoor radon greater than 4 pCi/L) | Every home is above 4 |
| Zone 2 | Moderate predicted potential (2–4 pCi/L predicted average) | Homes are “safe enough to skip testing” |
| Zone 3 | Lower predicted potential (less than 2 pCi/L predicted average) | Radon cannot be high in your house |
Critical EPA caveat (paraphrased for clarity): Use the map to prioritize education, building codes, and programs. Do not use it alone to decide whether *your* home needs a test. Test.
Why “low zone” homes can still be high
Radon entry is local. Soil gas pathways, sump pits, renovations that change pressure, and tightly sealed newer homes can all raise indoor levels even where county averages look modest. Conversely, a Zone 1 county still contains homes that test low. Variation within a ZIP is normal.
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How to look up risk information for your area (practical path)
Use this checklist instead of hunting for a magic ZIP number:
1. Find your county on the EPA zone map (links above) and note Zone 1 / 2 / 3.
2. Open your state radon program page via EPA’s state supporting documents list or the National Radon Program Services / state contacts (Kansas State University cooperative partnership with EPA).
3. Check whether your state publishes local maps, ZIP summaries, or downloadable tables—and read their footnotes (sample size, year, method).
4. Order or schedule a test for the lowest lived-in level of *your* home—regardless of zone.
5. If results are elevated, contact credentialed mitigation help (state list, NRPP, or NRSB as applicable).
Helper panel fields (if/when an on-site tool returns)
If Radon.org later ships a documented lookup, results should show:
| Field | Requirement |
|---|---|
| Input | ZIP and/or county |
| Output | Zone or relative potential, or “insufficient data” |
| Source citation | Named dataset + date accessed |
| Limitation line | “Not an indoor measurement of your home” |
| Primary CTA | Test your home → kits / detectors |
| Secondary CTA | State contact / free kits |
Avoid score widgets that imply lot-level certainty.
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How to run a basic home test (quick orientation)
You do not need a ZIP average to start. For a typical owner-occupied house:
1. Pick the lowest level people use regularly (finished basement, or first floor if the basement is unused storage only—follow your kit’s instructions and any state guidance).
2. Place the collector about 2–3 feet off the floor when the kit says so, away from drafts, exterior doors, humidifiers, and sump turbulence unless the instructions say otherwise.
3. Close-building conditions matter for many short-term real-estate protocols; DIY screening kits still deserve a fair, undisturbed placement period.
4. Record start/stop times and return the kit to the lab by the deadline (mail-in kits expire).
5. Read the lab report in pCi/L and compare to EPA’s 4 pCi/L action level and the 2–4 range.
6. If results are high or borderline, run a follow-up test (often longer-term) before major spend, unless a professional protocol already requires action.
Continuous digital monitors can supplement kits for ongoing awareness; they are not automatically accepted as closing tests. See the detector roundup for feature tradeoffs.
Interpreting home test results (the part that matters)
Radon is reported in picocuries per liter (pCi/L) of air in the U.S.
| Result range (typical EPA consumer framing) | Sensible next step |
|---|---|
| ≥ 4 pCi/L | Plan mitigation; confirm with appropriate follow-up testing |
| 2–4 pCi/L | Consider action; many homeowners retest and evaluate options |
| < 2 pCi/L | Lower concern *today*—still retest after major changes or on a periodic schedule |
There is no known completely safe indoor radon level; lower is better. Short-term tests can swing with weather—follow kit instructions and consider longer-term confirmation when results are near decision thresholds.
Choose a testing approach:
- Ultimate guide to radon test kits
- Long-term radon test kits
- Free / low-cost kit programs
- Continuous monitors: digital detector roundup
Basement-focused tips: radon basement risks and solutions.
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If levels are high: mitigation basics
When indoor radon stays elevated, a certified mitigation system (often active soil depressurization) is the standard fix. Typical homeowner path:
1. Confirm elevated results with a sound follow-up test.
2. Hire a credentialed mitigator (state license where required; otherwise NRPP/NRSB or equivalent).
3. Install the system (often completed in a day for many houses).
4. Retest after the system runs as instructed.
5. Maintain the fan/alarm and retest periodically.
Sealing major entry points can help as part of a designed system; sealing alone is rarely enough for high levels.
Finding help: Start with your state radon program contact list, then national directories such as NRPP and NRSB where relevant to your state.
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State and local programs (who to call)
State and county radon programs commonly provide:
- Hotlines and email help
- Zone explanations and local maps
- Free or discounted test kits (varies by state and funding)
- Lists of certified testers and mitigators
- Guidance for schools, rentals, and new construction
National starting points
- State radon contact directory (sosradon.org)
- EPA radon consumer hub: epa.gov/radon
- CDC radon page for health context: cdc.gov/radon
Program details differ: some states emphasize landlord testing rules; others emphasize free kits during National Radon Action Month (January). Always verify current offers on the official state site.
We intentionally do not duplicate thin per-state doorway pages here. Link out to enriched local resources when they add unique value; otherwise send readers to the official program.
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Community awareness (optional, keep short)
January is often recognized as National Radon Action Month. EPA and partners publish shareable materials; local health departments and cooperatives can distribute multilingual guides. Community outreach helps renters and lower-income households access kits—but awareness still ends with a measurement.
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Recommended path for most homeowners
1. Note your EPA county zone for context only.
2. Test the lowest lived-in level (kit, continuous monitor, or pro).
3. Compare results to 4 pCi/L (and the 2–4 range).
4. If elevated, mitigate with credentialed help and retest.
5. Retest after renovations, HVAC changes, or on a periodic schedule.
Maps inform. Tests decide.
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Frequently asked questions
Does a ZIP code tell me my home’s radon level?
No. ZIP- or county-level summaries describe area patterns or predicted potential. Only a test of indoor air measures *your* home.
What do EPA radon zones mean?
They classify counties by predicted average indoor radon potential: Zone 1 highest, Zone 2 moderate, Zone 3 lower. They are planning tools—not home diagnoses.
Should I test if my area is Zone 3 / “low potential”?
Yes. EPA’s zone map is not a reason to skip testing. High homes occur in every zone category.
How often should I retest?
After an initial test, many households retest every couple of years, after mitigation, and after major structural or HVAC changes. Follow your state program or mitigation contractor if you have a system.
Where can I get a free or low-cost kit?
Check your state radon program and Radon.org’s free/low-cost kits page. Availability changes with funding and season.
What radon level requires action?
EPA consumer guidance: fix homes at or above 4 pCi/L, and consider action between 2 and 4 pCi/L. Confirm with appropriate testing before spending on mitigation.
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Summary
Searching “radon levels by zip code” is a smart first instinct—but the trustworthy answer is almost always: your ZIP is incomplete information. Use the EPA Map of Radon Zones, your state program, and a real test. When you are ready to choose equipment, see our test kit guide and digital detector roundup.