Is radon high in San Luis Obispo County, California?

Low. The model predicts a long-term basement average of 1.6 pCi/L in San Luis Obispo County (close to the US average of 1.8 and close to the California average of 1.5). That is below the EPA's 2 pCi/L "consider fixing" threshold, though individual homes still vary. Ranked 19 of 58 California counties.

Should I test for radon in San Luis Obispo County?

Yes, once. The EPA recommends testing every home regardless of area, and the model's ZIP-level predictions in San Luis Obispo County already range from 1.3 to 2.0 pCi/L. A short-term kit costs little and settles the question for your house.

What does EPA Radon Zone 2 mean for San Luis Obispo County?

Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and classifies whole counties. The newer model's predicted average of 1.6 pCi/L does not line up with Zone 2, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

How much does radon mitigation cost in San Luis Obispo County?

A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; California quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

Radon levels in San Luis Obispo County, California

LowEPA Zone 2

Predicted long-term basement average of 1.6 pCi/L (model estimate) across 18 ZIP codes - close to the US average of 1.8, close to the California average of 1.5. Ranked #19 of 58 California counties.

Test San Luis Obispo County, CA once anyway - radon varies house to house

The predicted basement average here is 1.6 pCi/L, below the EPA's 2 pCi/L "consider fixing" threshold. That's good news for the area - but the EPA still recommends every home be tested, because foundation cracks, soil pockets and ventilation make one house very different from its neighbor. One inexpensive kit settles it.

Get a short-term test kit →Or track it with a continuous monitor

We may earn a commission from Amazon at no extra cost to you.

Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.

1.6 ± 0.07

pCi/L predicted basement mean (model SD)

1.0 ± 0.09

pCi/L predicted upstairs (above-ground) mean

1.3-2.0

range of ZIP-level basement predictions in the county

What this means for San Luis Obispo

The typical San Luis Obispo County home is predicted below 2 pCi/L, the lowest band. That is the best case an area can show - but it describes the average house, and the ZIP-level predictions within the county still span 1.3 to 2.0 pCi/L.

Note that the EPA classifies San Luis Obispo County as Zone 2 while the newer model predicts 1.6 pCi/L. The zone map predates two decades of test data; where they disagree, we grade on the model but show both. County figures weight each ZIP by its 2010 Census population, so they describe where people live rather than empty land.

Comparable California counties: Ventura County (1.6), San Benito County (1.6), Butte County (1.6), Shasta County (1.6). The state's highest is Mono County at 2.7 pCi/L.

ZIP codes in San Luis Obispo County

Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.

ZIP	Basement	Upstairs	Grade
93446	1.8 ± 0.06	1.3	Low
93405	1.5 ± 0.07	0.9	Low
93422	2.0 ± 0.06	1.5	Moderate
93420	1.8 ± 0.06	1.1	Low
93401	1.6 ± 0.07	0.9	Low
93444	1.6 ± 0.06	0.8	Low
93402	1.3 ± 0.07	0.5	Low
93433	1.3 ± 0.07	0.6	Low
93442	1.4 ± 0.07	0.6	Low
93465	1.7 ± 0.07	1.2	Low
93449	1.4 ± 0.06	0.8	Low
93445	1.5 ± 0.05	0.7	Low
93428	1.4 ± 0.08	0.6	Low
93430	1.3 ± 0.09	0.6	Low
93453	1.7 ± 0.07	1.0	Low
93461	1.9 ± 0.07	1.1	Low
93432	1.8 ± 0.07	1.3	Low
93452	1.4 ± 0.07	0.7	Low

If your test comes back at 4 pCi/L or higher

Mitigation is a routine job: a fan-driven pipe that vents soil gas from under the slab to above the roofline, typically $800-$2,500 installed (typical range; local quotes vary). Use certified professionals: EPA find-a-professional. Read the full mitigation guide.

San Luis Obispo County radon questions

Is radon high in San Luis Obispo County, California?: Low. The model predicts a long-term basement average of 1.6 pCi/L in San Luis Obispo County (close to the US average of 1.8 and close to the California average of 1.5). That is below the EPA's 2 pCi/L "consider fixing" threshold, though individual homes still vary. Ranked 19 of 58 California counties.
Should I test for radon in San Luis Obispo County?: Yes, once. The EPA recommends testing every home regardless of area, and the model's ZIP-level predictions in San Luis Obispo County already range from 1.3 to 2.0 pCi/L. A short-term kit costs little and settles the question for your house.
What does EPA Radon Zone 2 mean for San Luis Obispo County?: Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and classifies whole counties. The newer model's predicted average of 1.6 pCi/L does not line up with Zone 2, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.
How much does radon mitigation cost in San Luis Obispo County?: A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; California quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

← All California counties · How to test · Radon in a home sale · Methodology