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RADON411

Independent U.S. radon data

Radon levels by county and ZIP code, and how to test and fix your home

Radon411 is an independent U.S. radon data site: the EPA radon zone and reported radon tests for every county, plain guides to radon testing and radon mitigation, and certified radon professionals with their published certifications. The Radon Action Brief, a dated PDF report for one county, is $8.99 through January 31, then $25.

See the radon levels for your county or ZIP code

Radon products

Every radon test kit, monitor and fan we cover

Each one has its own page with the figures its maker publishes, marked where we could read none, and for a kit or a monitor, how it measures and its independent test status.

See all products

Compare up to four side by sideWhich test to use

Radon in numbers

Radon in 30 seconds

A colorless, odorless gas from the soil, and the second leading cause of lung cancer. Testing is the only way to know.

Radon data and sources

  • About21,000a year

    lung cancer deaths from radon (EPA).

    How radon causes lung cancer

  • Nearly1 in 15U.S. homes

    has elevated radon, EPA estimates.

    How to test your home

  • 4pCi/L

    EPA's action level: fix at or above.

    What your level means

Try it

Read a radon result, or your state against the country

Move the reading to see what EPA says about it, or pick a state to see its share of high tests, its rank and its tests beside the country's.

Read a result for any U.S. home

Starts at EPA's action level

4.0pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 4.0 pCi/L

At or above 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. 36.3% of the country's reported tests reached 4 pCi/L, 2006 to 2015.

Interpret this readingWhat a fix costs

Start here

Start with your situation

Choose the one closest to yours. Each opens the guide written for it.

Your area

Radon zones and tests for all 3,231 U.S. counties

EPA puts every county in one of three zones by its predicted average indoor radon level. A zone is a prediction for the whole county, not a reading of any home. Every state and county has a free page: choose yours on the map, type it, or find it in the list.

Map of the United States with every county shaded by its EPA radon zone: Zone 1 red, Zone 2 amber, Zone 3 pale.AlabamaAlaskaArizonaArkansasCaliforniaColoradoConnecticutDelawareDistrict of ColumbiaFloridaGeorgiaHawaiiIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMaineMarylandMassachusettsMichiganMinnesotaMississippiMissouriMontanaNebraskaNevadaNew HampshireNew JerseyNew MexicoNew YorkNorth CarolinaNorth DakotaOhioOklahomaOregonPennsylvaniaPuerto RicoRhode IslandSouth CarolinaSouth DakotaTennesseeTexasU.S. Virgin IslandsUtahVermontVirginiaWashingtonWest VirginiaWisconsinWyoming
Predicted: EPA Map of Radon Zones, every U.S. county. Choose a state in the field above or the list to open its page.Choose a state to open its page.
  • Zone 1Highest predicted potential, predicted greater than 4 pCi/L1,071counties
  • Zone 2Moderate predicted potential, predicted 2 to 4 pCi/L1,034counties
  • Zone 3Lower predicted potential, predicted less than 2 pCi/L1,033counties
  • No zone on fileEPA has published no zone for these93counties

Measured: tests of other buildings are on file for 2,863 counties, never a reading of your home.

An EPA radon zone predicts a whole county. It is not intended to determine whether any individual home should be tested: homes with elevated levels occur in all three zones, and EPA recommends testing every home regardless of zone.

Open the radon map

The states compared

Measured: each state’s counties’ reported tests added up, 2006 to 2015. Choose the figure, then open a state.

  1. 1Nebraska59.7%
  2. 2Iowa59.4%
  3. 3South Dakota58.8%
  4. 4North Dakota56.3%
  5. 5Ohio52.9%
  6. 6Colorado48.8%
  7. 7Wisconsin48.2%
  8. 8Montana47.4%
  9. 9Kentucky46.4%
  10. 10Wyoming45.3%
  11. 11Minnesota45.0%
  12. 12Pennsylvania44.6%
View all 47 states by share at 4+ pCi/L
  1. 13Illinois44.3%
  2. 14Utah41.6%
  3. 15Idaho41.3%
  4. 16Indiana39.6%
  5. 17West Virginia37.7%
  6. 18Maine37.6%
  7. 19Tennessee33.4%
  8. 20New Hampshire32.3%
  9. 21Missouri31.7%
  10. 22Virginia30.7%
  11. 23New Mexico30.3%
  12. 24Oregon26.9%
  13. 25Connecticut26.8%
  14. 26Michigan26.8%
  15. 27Washington25.9%
  16. 28New York25.2%
  17. 29Maryland24.9%
  18. 30North Carolina24.1%
  19. 31Nevada23.7%
  20. 32Georgia23.7%
  21. 33Rhode Island23.7%
  22. 34Massachusetts23.4%
  23. 35Florida22.9%
  24. 36Arkansas22.5%
  25. 37Alabama22.0%
  26. 38Vermont21.8%
  27. 39Alaska21.5%
  28. 40South Carolina19.8%
  29. 41Delaware17.6%
  30. 42Arizona17.6%
  31. 43Oklahoma12.6%
  32. 44Texas11.0%
  33. 45California10.6%
  34. 46District of Columbia8.5%
  35. 47Louisiana2.8%
Every state and territory, by region56
Northeast9
Midwest12
South17
West13
Territories5

Four steps

Learn, test, fix, find a pro

The whole path, from a county report to a confirmed fix in your own home.

  1. Learn

    Know what radon is

    What radon is, how it gets indoors, and why a county zone is not a reading for your home.
    Learn about radon

  2. Test

    Test the building you live in

    Short-term or long-term, where the device goes, and closed-house conditions.
    How to test

  3. Fix

    Bring a high level down

    How a mitigation system works, and the retest that confirms it.
    How mitigation works

  4. Find a pro

    Hire a certified professional

    Measurement and mitigation professionals by state, with their certifications.
    Find a professional

Guides

A guide for every topic

Plain answers on what radon is, how to test a home and how to bring a high level down.

Lead guide, learn

What is radon gas? Where it comes from and how it gets indoors

Radon gas is a naturally occurring radioactive gas, with no color, smell or taste, that forms as uranium breaks down in rock, soil and water. It dilutes quickly outdoors but can build up inside buildings, and a test is the only way to know the level in yours.

See all guides, by topic

Get help

People and tools for the job

Radon411 does not certify anyone or perform tests. It lists what is published, so you can compare and choose.

  • Professionals

    Certified radon professionals

    2,035 measurement and mitigation businesses are listed, each with its certification shown the way the certifying body published it.

    Find a professional

  • Products

    Test kits, monitors and fans

    62 radon products are compared on their published specifications, each on its own page with how it works and, for a monitor, its independent test status. Affiliate links are labeled where they appear.

    See every product

Our standard

How Radon411 works

  • Published figures only

    Every radon figure on Radon411 is a public agency's own: EPA's zones, CDC's reported tests, a state program's page. Where Radon411 adds the arithmetic, the page says so. Where no figure exists for a place, the page says that too.

    How each figure is read

  • Written and dated

    The Radon411 Editorial Team writes every guide, question and level explainer, checks it against EPA, CDC, WHO and USGS material, and dates it on the page. No invented expert, no borrowed credential.

    How we work

  • Independent

    Featured directory listings are paid placements and say so where they appear. Product links go to Amazon as affiliate links, disclosed on every product page. Nothing else is sponsored.

    The affiliate disclosure

Your next step

Look up the place you care about

Every state and county has a free report: its predicted zone, the tests on file and what to do next.

Find your county