Ontario, CA Radon Levels
Check local Ontario radon levels and find certified testing and mitigation professionals to keep your home safe
Ontario, CA Radon Facts
EPA Radon Zone
Zone 2 — Moderate Risk
2–4 pCi/L (Zone 2)
County
San Bernardino County, CA
Zip Code
91758
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.
Need Radon Mitigation or Testing in Ontario?
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- Matches You with State-Licensed San Bernardino County Pros
1-800-299-3578
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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 in California with the most user-submitted radon test data, ranked by number of submissions.
| 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 |
| Bishop | 6.25 pCi/L | 4 |
| Oakland | 5.00 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 |
| Sacramento | 4.33 pCi/L | 3 |