Radon Levels Parent Guide

Radon Levels: What 2.0, 4.0, and 8.0 pCi/L Mean

Use this page to translate a radon test result into a practical next step, then open state and county pages backed by official measurement tables, CDC summaries, or official radon maps.

Interpret My Number Browse State Maps

Fast Answer

Under 2.0 pCi/L

Lower concern, but retest periodically because home levels change.

2.0 to 3.9 pCi/L

Retest or track long-term. Reduction can still be worth considering.

4.0+ pCi/L

Start mitigation planning. This is the main EPA action threshold.

Official County Data

735 of 735 listed county pages use official radon support

Measured counties use official state tables or CDC Tracking summaries. Map-classified counties use official radon-potential categories when a county pCi/L table is not published.

100%

official support

Measured counties

718

State tables

370

Map classified

More county detail

CDC Environmental Public Health Tracking Network Radon Tests from Labs: 348 Pennsylvania DEP Radon Test Data by ZIP Code: 50 Virginia Department of Health Radon Testing Results: 45 New York State Department of Health Residential Radon Test Data: 42 Illinois IEMA-OHS Licensed Radon Measurement Dashboard: 39 Minnesota Department of Health Indoor Air Unit Radon Test Data: 34 Tennessee Environmental Public Health Tracking Radon Data: 31 Wisconsin Department of Health Services Indoor Radon Test Results: 30 Iowa HHS Radon Dashboard County Metrics: 29 Colorado Environmental Public Health Tracking Pre-Mitigation Radon Test Results: 25 New Jersey DEP Radon Potential Municipality Tier Table: 17 Kansas Environmental Public Health Tracking Radon Data: 14 Missouri DHSS Residential Radon Testing in Missouri: 12 North Carolina DHHS Radon Data Map: 12 Utah EPHT Radon Test Kit Results: 7

Open Official-Data States First

Route from the national threshold to state-specific radon data

Some states publish county measurements, while others are best read through CDC Tracking or official radon-potential maps. Start with the states below when you need county pages with clearer public data behind the recommendation.

IA Iowa HHS medians NC NCDHHS highs PA DEP ZIP data IL state results CO CDPHE data UT EPHT results

State measurements

Iowa HHS publishes county median radon values. Osceola County, IA shows an 11.4 pCi/L median, so its page should be opened before treating Iowa as only a zone-map question.

Highest measured examples

North Carolina DHHS maps the highest measured radon level by county. Rutherford County, NC shows 681 pCi/L as a high-end county signal, not a county average.

CDC and map coverage

CDC summaries and official state/federal radon-potential maps still help when a state does not publish a county measurement table. Use them as context, then let a home test decide.

National Data Guide

Start with the national action threshold, then open states with the strongest county evidence.

This page connects the plain 2.0, 4.0, and 8.0 pCi/L answer to state hubs where county evidence is strongest: 735 of 735 surfaced county pages have official evidence, with 718 measured county summaries and 17 official map-classification summaries.

718

measured counties

Official source base

Official source base: 370 county summaries come from state-specific or federal measurement tables, 348 use CDC Tracking, 17 use official state or federal map classifications, and 0 need more county-specific detail. That helps users tell the difference between a county with reported test data and a broader map guide.

How to use it

Most surfaced county pages now have official evidence behind them, so users can start with source-backed pages instead of a generic national answer.

Where county detail is lighter

Some counties still depend on broader federal summaries or state pages without county pCi/L metrics. In those cases, use the county page as context and let a fresh home test control the decision.

Open these state hubs first

States with the strongest county evidence

Ranked by official coverage, measured county pages, elevated/high county count, and state measurement strength.

63 CDC summaries

Strong evidence

63/63 counties with official support

63 measured, 0 map-classified

63 elevated/high, 60 high

OH is a strong starting point because it has 60 counties with high measured radon signals and 0 state measurement summaries.

50 state measurement summaries

Start here

50/50 counties with official support

50 measured, 0 map-classified

49 elevated/high, 48 high

PA is a strong starting point because it has 48 counties with high measured radon signals and 50 state measurement summaries.

48 CDC summaries

Strong evidence

48/48 counties with official support

48 measured, 0 map-classified

47 elevated/high, 42 high

IN is a strong starting point because it has 42 counties with high measured radon signals and 0 state measurement summaries.

45 state measurement summaries

Start here

45/45 counties with official support

45 measured, 0 map-classified

40 elevated/high, 31 high

VA is a strong starting point because it has 31 counties with high measured radon signals and 45 state measurement summaries.

42 state measurement summaries

Start here

42/42 counties with official support

42 measured, 0 map-classified

37 elevated/high, 31 high

NY is a strong starting point because it has 31 counties with high measured radon signals and 42 state measurement summaries.

39 state measurement summaries

Start here

39/39 counties with official support

39 measured, 0 map-classified

38 elevated/high, 36 high

IL is a strong starting point because it has 36 counties with high measured radon signals and 39 state measurement summaries.

34 state measurement summaries

Start here

34/34 counties with official support

34 measured, 0 map-classified

33 elevated/high, 25 high

MN is a strong starting point because it has 25 counties with high measured radon signals and 34 state measurement summaries.

30 state measurement summaries

Start here

30/30 counties with official support

30 measured, 0 map-classified

28 elevated/high, 25 high

WI is a strong starting point because it has 25 counties with high measured radon signals and 30 state measurement summaries.

Direct Answer

What radon level should homeowners act on?

In US guidance, 4.0 pCi/L or higher is the main action threshold for fixing a home. Results from 2.0 to 3.9 pCi/L still deserve attention because radon risk is not zero below 4.0; retest, track long-term, or consider reduction depending on the home and situation.

Evidence	Value
Under 2.0 pCi/L	Lower concern; keep periodic testing
2.0 to 3.9 pCi/L	Retest, track, or consider reduction
4.0+ pCi/L	EPA action threshold for fixing the home
8.0+ pCi/L	High reading; prioritize mitigation planning

Sources

Result Meaning

What your radon number means

No result yet? Read the testing guide

Reading

Plain meaning

Next step

Under 2.0

Below the range where most homeowners start pricing mitigation, but not a permanent all-clear.

Keep the result, retest after major home changes, and consider periodic monitoring.

2.0-3.9

Borderline range. It is below the main EPA action threshold, but risk is not zero.

Retest with a valid setup, use a long-term monitor, or price mitigation if the home has compounding risk.

4.0-7.9

Elevated result. This is where mitigation planning becomes the practical next step.

Confirm the reading if needed, then compare local mitigation costs and contractor requirements.

8.0+

High reading. Waiting usually creates more risk and more negotiation friction.

Prioritize mitigation quotes. In a real-estate deal, turn the local cost range into a repair or credit ask.

4.0+ Reading

Get a Local Action Plan

Use your ZIP, foundation type, and result band to open the right county cost page.

Buying or Selling

Calculate a Seller Credit

Turn a local mitigation range into a repair ask, credit ask, or quick-close fallback.

Trust & Sources

Read the Methodology

See how public EPA, state, housing, and cost data are used across RadonVerdict.

EPA Zone Context

EPA zones are map context, not your home result

EPA radon zones estimate county-level potential. They are useful for deciding how seriously to treat local risk, but the reading inside one basement, slab home, or crawl-space home can be higher or lower than the county prediction.

1070

Zone 1 counties

Highest predicted average potential. Testing and mitigation planning deserve early attention.

1035

Zone 2 counties

Moderate predicted average potential. Borderline readings should not be dismissed.

1033

Zone 3 counties

Lower predicted average potential. Direct testing is still the deciding evidence.

Open the official EPA Map of Radon Zones

State and County Maps

Browse radon levels by state

735 county pages currently available in the state map directory.

AK 2 counties AL 15 counties AR 2 counties AZ 9 counties CA 19 counties CO 25 counties DE 1 counties FL 7 counties GA 14 counties IA 29 counties ID 9 counties IL 39 counties IN 48 counties KS 14 counties KY 19 counties MA 10 counties MD 12 counties ME 12 counties MI 15 counties MN 34 counties MO 12 counties MT 10 counties NC 12 counties ND 8 counties NE 10 counties NH 6 counties NJ 17 counties NM 7 counties NV 4 counties NY 42 counties OH 63 counties OR 2 counties PA 50 counties RI 3 counties SC 5 counties SD 6 counties TN 31 counties TX 2 counties UT 7 counties VA 45 counties VT 1 counties WA 6 counties WI 30 counties WV 12 counties WY 9 counties

Sources and limits

This page uses EPA radon action-level guidance and EPA zone data for public-risk context. It is not medical advice, legal advice, or a substitute for a valid home radon test. If you already have a result, your own measured level matters more than the county zone.

EPA radon resources WHO Handbook on Indoor Radon RadonVerdict methodology

Editorial and Data Transparency

Author: RadonVerdict Data Team (Public Data and Cost Modeling)
Content Review: Source-level dates shown below
Data Retrieved At: Source-level dates below

Primary Sources

EPA Map of Radon Zones (retrieved 2026-02-21)
EPA A Citizen's Guide to Radon (retrieved 2026-05-05)
CDC Environmental Public Health Tracking - Radon Testing (retrieved 2026-05-05)
Angi Radon Mitigation Cost Guide (retrieved 2026-02-21)