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Radon Levels in San Francisco County, California

EPA puts San Francisco County in Zone 2, its middle radon zone. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

Predicted
Zone 2Moderate predicted potential
Measured
2.8%of 246 tests reported to CDC (2008 to 2017) were at or above 4 pCi/L
Your home
Test to knowNo area figure here is a reading of your home.

The data

San Francisco County, At a glance

San Francisco County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.

What EPA predicts hereScreening level, geology

EPA predicts an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³) across the county as a whole.

USGS geologic potential: Moderate across 90% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for San Francisco County, 2008 to 2017, laboratory

Tests reported
246
At or above 4 pCi/L
2.8%
Median result
0.5 pCi/L
Reported results by concentration band, San Francisco County, 2008 to 2017, laboratory
Under 2 pCi/L: 89%2 to 4 pCi/L: 8%4 pCi/L and above: 3%

Of 246 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, San Francisco County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L21888.6%
2 to 4 pCi/L218.5%
4 pCi/L and above72.8%

CDC publishes this figure only for counties here, so there is no state or national number to compare San Francisco County, California with.

What these figures count

Distribution of radon tests reported to CDC, not this house. People testing before a sale, or because they suspect a problem, are over-represented in any reported testing data.

The figures at the top are for 2008 to 2017 (laboratory totals): a percentage there is a share of radon tests reported to CDC for San Francisco County over 2008 to 2017, laboratory, and a percentage in a view below is a share of the tests reported for the year or period it names. It is not a share of homes in San Francisco County, and it is not a random sample: it counts only the tests people chose to run and that were reported.

CDC works out the shares and the median over pre-mitigation tests, counting a test not marked as before or after mitigation as one of them (246 for 2008 to 2017, laboratory). The median is the middle result of those tests, not of buildings. CDC also reports the number of buildings tested (174), a different count, so the two totals are not interchangeable.

San Francisco County's own published CDC figures beside those of the counties that border it, for the same period.

Each figure is that county’s own published CDC figure for 2008 to 2017, laboratory, counting radon tests reported to CDC, not homes. San Francisco County is this page. Nothing is averaged or combined across counties. The test count beside each county is CDC’s published number of pre-mitigation tests behind its figures. Figures from few tests can swing widely from year to year. Every California county’s own figure is in the California county table.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

Radon Action Brief

National Radon Action MonthPre-sale

San Francisco County's radon brief, in one dated file.

  • Your area's radon record, explained.
  • Your plan to test this week.
  • Fix costs and pros near you.

Save 64%Sale price: $8.99Price after the sale: $25Ends Jan 31Then $25

Get the San Francisco County BriefSee a free sample

Area data, not a test of the building.

Local help

San Francisco County, Local resources

Radon testing and mitigation in San Francisco County

Who tests and fixes radon in San Francisco County: listed businesses, California's radon program and test kits.

What it means

San Francisco County, Questions

Questions about radon in San Francisco County

Common questions

8 questions, answered from the figures above

How do I get a radon test in San Francisco County?

EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. No radon testing business listed on Radon411 has an address in San Francisco County or names it as a service area yet. The California radon program is the place to ask about certified testers and any test kit offer it runs.

Radon testing: how to test a homeRadon test kits comparedFree and low-cost kits by stateRadon Action Month checklistCalifornia radon program

Are radon levels high in San Francisco County?

Over the 2008 to 2017 laboratory totals, 2.8% of the radon tests reported to CDC for San Francisco County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.5 pCi/L. That is a share of reported tests, not of homes. EPA places San Francisco County in Zone 2, moderate predicted potential, a predicted average indoor screening level 2 to 4 pCi/L. Homes with elevated levels occur in all three zones, so the figures describe the area, not your house. Testing is the only way to know the radon level in a specific building.

Radon levels: what a result meansWhat is radon?Radon levels in California

Who does radon mitigation in San Francisco County?

No listed mitigator names San Francisco County as a service area yet; the California directory lists 4 companies. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional. Your state radon program is the place to check whether California requires one.

Radon mitigation: how it worksRadon mitigation costRadon mitigation systemsMitigators in California

What EPA radon zone is San Francisco County in?

EPA places San Francisco County, California in Zone 2, which EPA describes as moderate predicted potential for the area. A zone is a prediction for the whole county and never determines whether a particular home should be tested. EPA recommends testing every home regardless of zone.

Should I test my home in San Francisco County?

Yes. 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 recommends considering a fix when the level is between 2 and 4 pCi/L. How to test a home.

When is the best time of year to test?

EPA says short-term tests stay in the home from 2 to 90 days and that all radon tests should run a minimum of 48 hours; long-term tests stay more than 90 days. EPA's guides do not name a best season: they say radon levels tend to vary from day to day and season to season, so a long-term test is more likely than a short-term test to tell you the year-round average.

What does it cost to test?

EPA's Citizen's Guide calls testing easy and inexpensive, and EPA's Home Buyer's and Seller's Guide says passive short-term and long-term devices are generally inexpensive, while active devices may cost more. No national average price is published for this, so Radon411 does not give one. What testing costs.

Which counties border San Francisco County?

San Francisco County borders 1 county, derived from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county's report can be relevant.

If you own, buy, sell or rent

What these figures mean for each reader, with the guide that covers it

San Francisco County in figures

The figures above, said in words

What the published data says about San Francisco County, in words. A zone and a share of tests describe an area, never the level in any one home.

    • Predicted

      Predicted

      EPA places San Francisco County in Zone 2, moderate predicted potential, as it does 28 other counties of California's 58.

      Its one bordering county, San Mateo County, is in Zone 2.

  • Reported tests

    Measured

    CDC publishes no annual figure for San Francisco County; its figure is a laboratory total for 2008 to 2017: 2.8% of 246 reported tests were at or above 4 pCi/L.

  • Local record

    California's radon program is the California Indoor Radon Program, run by California Department of Public Health; its contacts are under Local resources.

    The county's largest incorporated place is San Francisco; the figures here cover them as part of the county.

Products

San Francisco County, Products

Testing and mitigation products

Whatever the figures for San Francisco County show, only a test tells you about one home.

Test kits and monitors42

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Best radon monitors for San Francisco County homes, compared

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San Francisco County, Bordering counties

Counties bordering San Francisco County

Calculated by Radon411
Why bordering counties matter

One county shares a boundary with San Francisco County, computed from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county’s report can be worth reading alongside this one.

San Francisco County, Cities and towns

Cities and towns in San Francisco County

The radon figures on this page are for San Francisco County as a whole. They do not differ by city or town.

  • San Francisco

One incorporated place, as listed in the U.S. Census Bureau’s 2020 place reference files.

San Francisco County, Next steps

What to do next

Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.