National radon map

counties: 3,231counties
with an EPA zone on file: 3,138with an EPA zone on file
with reported measurements: 2,862with reported measurements

3,230 of 3,231 counties are drawn on the map; no boundary is on file for Falls Church city, VA.

The interactive map and the filters need JavaScript. The static map, the zone key and the state-by-state table below work without it, and each state links to every county report.

Map of the United States, every county shaded by its EPA radon zone. 1,070 counties are Zone 1, 1,034 are Zone 2, 1,033 are Zone 3, and 93 have no zone on file.

Pick a county

Click a county on the map, or choose one from the list, to see its zone, its reported measurements and a link to its full report.

Zone 1: Highest predicted potentialHighest predicted potential
Zone 2: Moderate predicted potentialModerate predicted potential
Zone 3: Lower predicted potentialLower predicted potential
Zone not available: No EPA zone on fileNo classification published

3,230 of 3,230 counties

Show patterns

Adds thin lines to Zone 1 and Zone 2 on the map and in the key.

Key

What the shading means

A colour on this map is a prediction for a whole county: darkest for Zone 1, palest for Zone 3. Every zone also carries its number and a written label, so the map reads without colour, and the list beside the map names the zone of every county.

Zone 1: Highest predicted potential: Highest predicted potential. Predicted average indoor screening level greater than 4 pCi/L (greater than 150 Bq/m³).
Zone 2: Moderate predicted potential: Moderate predicted potential. Predicted average indoor screening level 2 to 4 pCi/L (75 to 150 Bq/m³).
Zone 3: Lower predicted potential: Lower predicted potential. Predicted average indoor screening level less than 2 pCi/L (less than 75 Bq/m³).
Zone not available: No EPA zone on file: Radon411 has no EPA zone on file for the county. This is not the same as Zone 3: it means there is no classification, not that potential is low.

How EPA says this map should be used

An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.

EPA zone classifications: updated September 25, 2026.

Definitions

EPA's three zones, in full

The wording here is EPA's, used unchanged everywhere a zone appears on this site.

Zone 1: Highest predicted potential
Predicted potential
Highest predicted potential
Predicted average indoor screening level
greater than 4 pCi/L (greater than 150 Bq/m³)
Zone 2: Moderate predicted potential
Predicted potential
Moderate predicted potential
Predicted average indoor screening level
2 to 4 pCi/L (75 to 150 Bq/m³)
Zone 3: Lower predicted potential
Predicted potential
Lower predicted potential
Predicted average indoor screening level
less than 2 pCi/L (less than 75 Bq/m³)

EPA Map of Radon Zones, zone definitions
Zone	Predicted potential	Predicted average indoor screening level	Same level in Bq/m³
Zone 1: Highest predicted potential	Highest predicted potential	greater than 4 pCi/L	greater than 150 Bq/m³
Zone 2: Moderate predicted potential	Moderate predicted potential	2 to 4 pCi/L	75 to 150 Bq/m³
Zone 3: Lower predicted potential	Lower predicted potential	less than 2 pCi/L	less than 75 Bq/m³

A zone is not a measurement

By state

How much of each state is classified

Coverage, not radon levels: how many of each state's counties carry each layer. An unshaded county on the map above is a county with no classification on file.

Query the underlying values

EPA radon zone distribution and testing-data coverage by state
State	Counties	Zone 1	Zone 2	Zone 3	No zone on file	Counties with test data
Alabama (AL)	67	13	33	21	0	65
Alaska (AK)	29	0	5	20	4	25
American Samoa (AS)	3	0	0	0	3	0
Arizona (AZ)	15	0	15	0	0	13
Arkansas (AR)	75	0	14	61	0	61
California (CA)	58	2	29	27	0	56
Colorado (CO)	64	53	11	0	0	64
Connecticut (CT)	8	4	3	1	0	8
Delaware (DE)	3	0	1	2	0	3
District of Columbia (DC)	1	0	0	1	0	1
Florida (FL)	67	0	9	58	0	65
Georgia (GA)	159	4	55	100	0	139
Guam (GU)	1	0	0	0	1	0
Hawaii (HI)	5	0	0	5	0	0
Idaho (ID)	44	19	20	5	0	44
Illinois (IL)	102	56	43	3	0	102
Indiana (IN)	92	57	35	0	0	92
Iowa (IA)	99	99	0	0	0	99
Kansas (KS)	105	65	40	0	0	104
Kentucky (KY)	120	30	82	8	0	120
Louisiana (LA)	64	0	0	64	0	54
Maine (ME)	16	12	4	0	0	16
Maryland (MD)	24	8	9	7	0	24
Massachusetts (MA)	14	3	10	1	0	14
Michigan (MI)	83	9	32	42	0	83
Minnesota (MN)	87	68	19	0	0	87
Mississippi (MS)	82	0	8	74	0	0
Missouri (MO)	115	11	97	7	0	115
Montana (MT)	56	49	7	0	0	53
Nebraska (NE)	93	53	24	16	0	93
Nevada (NV)	17	9	7	1	0	16
New Hampshire (NH)	10	1	9	0	0	10
New Jersey (NJ)	21	7	11	3	0	21
New Mexico (NM)	33	7	26	0	0	30
New York (NY)	62	34	13	15	0	62
North Carolina (NC)	100	8	31	61	0	100
North Dakota (ND)	53	53	0	0	0	53
Northern Mariana Islands (MP)	4	0	0	0	4	0
Ohio (OH)	88	53	35	0	0	88
Oklahoma (OK)	77	0	9	68	0	55
Oregon (OR)	36	0	21	15	0	36
Pennsylvania (PA)	67	49	17	1	0	67
Puerto Rico (PR)	78	0	0	0	78	0
Rhode Island (RI)	5	2	2	1	0	5
South Carolina (SC)	46	1	8	37	0	46
South Dakota (SD)	66	48	18	0	0	64
Tennessee (TN)	95	39	32	24	0	95
Texas (TX)	254	0	39	215	0	150
U.S. Virgin Islands (VI)	3	0	0	0	3	0
Utah (UT)	29	7	22	0	0	29
Vermont (VT)	14	0	12	2	0	14
Virginia (VA)	133	62	28	43	0	132
Washington (WA)	39	7	14	18	0	39
West Virginia (WV)	55	20	29	6	0	55
Wisconsin (WI)	72	28	44	0	0	72
Wyoming (WY)	23	21	2	0	0	23

Counted above but not drawn on the map, because no boundary is on file for it: Falls Church city, VA.

Questions people ask

What is radon Zone 1?

Zone 1 is EPA's class for counties with highest predicted potential: a predicted average indoor screening level greater than 4 pCi/L. An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.

Every county's zone on the radon map

What is radon Zone 2?

Zone 2 is EPA's class for counties with moderate predicted potential: a predicted average indoor screening level 2 to 4 pCi/L. An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.

Every county's zone on the radon map

What is radon Zone 3?

Zone 3 is EPA's class for counties with lower predicted potential: a predicted average indoor screening level less than 2 pCi/L. An EPA radon zone describes predicted potential across a whole county. It is not intended to determine whether any individual home should be tested, and homes with elevated levels occur in all three zones. EPA recommends testing every home regardless of zone, and testing is the only way to know the radon level in a specific building.

Every county's zone on the radon map

Where is radon most common?

Radon is most common where the soil and rock carry more uranium, the areas EPA's Map of Radon Zones marks as highest potential, and indoors it is usually highest in basements and ground-contact rooms. Elevated levels have been found in every state and in all three zones, so any home can have a problem.

Where is radon most common?