Ontario, CA Radon Mitigation and Testing

Q: What EPA Radon Zone is Ontario in?

Ontario is in San Bernardino County, EPA Zone 2.

Q: How much does radon mitigation cost in Ontario?

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

San Bernardino County

EPA Zone 2

Located in San Bernardino County, Ontario residents in zip code 91758 have limited radon testing data available. California's generally lower radon risk doesn't eliminate the need for testing, especially in homes with below-grade areas or built on fill soils. Homeowners should consider radon testing to establish baseline levels for their properties.

Ontario, CA Radon Mitigation

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

Ontario, CA Radon Testing

Finding qualified radon testing professionals is the first step toward protecting your home.

Ontario Radon Facts

Key details about the radon risk profile for Ontario and the 91758 zip code area.

EPA Radon Zone

Zone 2 — Moderate Risk

County

San Bernardino County, CA

Zip Code

91758

Predicted Screening Level

2–4 pCi/L (Zone 2)

Ontario and the 91758 zip code are located in San Bernardino County, which has an EPA assigned Radon Zone of 2. A radon zone of 2 predicts an average indoor radon screening level between 2 and 4 pCi/L. The EPA recommends testing every home regardless of zone classification.

Radon FAQ for Ontario, CA

What EPA Radon Zone is Ontario in?

Ontario and the 91758 zip code are in San Bernardino 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.

How much does radon mitigation cost in Ontario?

Radon mitigation in Ontario 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 Ontario?

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.

Most Active Radon Markets in California

Cities with the most user-submitted radon test data in the state.

City	Avg User Radon Level	Submissions
Los Angeles	7.83 pCi/L	6
Mammoth Lakes	10.80 pCi/L	5
San Jose	4.20 pCi/L	5
Rancho Palos Verdes	8.00 pCi/L	4
Woodland Hills	7.67 pCi/L	3
South Lake Tahoe	6.33 pCi/L	3
Palos Verdes Peninsula	6.00 pCi/L	3
Bishop	5.67 pCi/L	3
Sacramento	4.33 pCi/L	3
Oakland	3.33 pCi/L	3
Fresno	10.00 pCi/L	2
Davis	8.00 pCi/L	2
Palo Alto	6.50 pCi/L	2
Studio City	6.50 pCi/L	2
Menlo Park	5.00 pCi/L	2
Truckee	5.00 pCi/L	2
Walnut Creek	4.00 pCi/L	2
San Diego	3.50 pCi/L	2
San Francisco	3.50 pCi/L	2
Belmont	20.00 pCi/L	1