Sources and method

Source

The EPA Map of Radon Zones page links a text version (xls, September 2025) and a map (pdf). EPA developed the map in 1993. Zone meanings are copied from the map legend.

What a zone is

EPA says the map is for targeting resources and radon-resistant building codes, and should not be used to determine if a home needs testing. Homes with elevated levels have been found in all three zones.

What we left out

The EPA file has two data sheets. They give different zones for these places, so we publish no page for them until that is settled. Ask your state radon office.

• Anchorage Municipality, Alaska: Zone 3 on the first sheet, Zone 2 on the second
• La Plata County, Colorado: Zone 1 on the first sheet, Zone 2 on the second
• Somerset County, Maryland: Zone 2 on the first sheet, Zone 3 on the second
• Macon County, Tennessee: Zone 1 on the first sheet, Zone 2 on the second
• Madison County, Tennessee: Zone 1 on the first sheet, Zone 3 on the second
• Marion County, Tennessee: Zone 2 on the first sheet, Zone 3 on the second
• Maury County, Tennessee: Zone 3 on the first sheet, Zone 1 on the second

Check

A script compared every published page against a fresh copy of the EPA file. If you find an error, write to the address on the about page.