Washington, MO Radon Levels

Q: What EPA Radon Zone is Washington in?

Washington is in Franklin County, EPA Zone 2.

Q: How much does radon mitigation cost in Washington?

Radon mitigation typically costs between $800 and $2,000. Most standard systems fall in the $1,000-$1,500 range.

Check local Washington radon levels and find certified testing and mitigation professionals to keep your home safe

Washington, MO Radon Facts

EPA Radon Zone Zone 2 — Moderate Risk 2–4 pCi/L (Zone 2)

County Franklin County, MO

Zip Code 63090

Located in Franklin County within the St. Louis Metro area, Washington sits on Mississippian limestone formations that create moderate-to-high radon potential. Testing data for zip code 63090 remains limited, though Missouri's karst geology often produces variable radon levels. The community's housing ranges from historic homes along the Missouri River to newer suburban developments, with basement foundations common throughout the area.

7.33

pCi/L area average

Above EPA Action Level

Franklin County average: 7.33 pCi/L, based on 3 user-submitted tests across 3 cities in the county. No homeowner readings have been submitted for Washington itself yet, so this county figure is the closest available benchmark. The EPA recommends taking action at or above 4.0 pCi/L.

4.0 EPA

10+

Washington, MO Radon Mitigation

Professional radon mitigation is the most effective way to permanently lower radon levels and protect your household.

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Radon Readings Near Washington, MO

No homeowner tests have been submitted for Washington yet. The closest cities with user-submitted radon data are shown below — explore them to gauge local conditions. Radon varies by home, so testing is the only way to know your level.

City	Distance	Avg User Level	Readings
Union	6.9 mi	13.00 pCi/L	1
Labadie	7.9 mi	4.00 pCi/L	1
New Haven	11.5 mi	5.00 pCi/L	1
Lake Saint Louis	21.3 mi	5.00 pCi/L	2
O Fallon	22.6 mi	7.75 pCi/L	4
Chesterfield	24.9 mi	5.00 pCi/L	1
Ballwin	26.0 mi	4.00 pCi/L	1
House Springs	26.6 mi	7.00 pCi/L	1

Franklin County Radon Profile

EPA mapping assigns Franklin County to Radon Zone 2, indicating moderate predicted indoor screening levels in the 2 to 4 pCi/L range based on regional geology. Homeowner-submitted tests from 3 cities in Franklin County average 7.33 pCi/L across 3 tests — above the EPA's 4 pCi/L action level, reinforcing the need for testing across the county. As the second leading cause of lung cancer in the U.S., radon warrants testing in every Franklin County home regardless of zone or a neighbor's results.

Radon FAQ for Washington, MO

What EPA Radon Zone is Washington in?

Washington and the 63090 zip code are in Franklin County, which has an EPA assigned Radon Zone of 2. A zone of 2 predicts an average indoor radon screening level between 2 and 4 pCi/L.

Why are radon readings shown from areas near Washington?

No homeowner radon tests have been submitted for Washington yet. Because radon is driven by regional soil and bedrock geology, readings from the closest cities—and the Franklin County average—are the best available indicator of local conditions until Washington homeowners submit their own results. The EPA still recommends testing every individual home, since levels can vary significantly from house to house.

How much does radon mitigation cost in Washington?

Radon mitigation in Washington typically costs between $800 and $2,000. Most homes with standard basements can be mitigated with a sub-slab depressurization system in the $1,000–$1,500 range. Factors that can increase cost include complex foundations, crawl spaces, or very high radon levels.

Should I test for radon if I'm buying a home in Washington?

Yes. Radon testing should be part of every home purchase. A short-term radon test is typically included as part of the home inspection process and costs $150–$250. If elevated levels are found, you can negotiate mitigation as part of the sale.