Radon testing, levels & next step in Los Angeles County, CA
Local service search answer: If you searched for radon gas testing, mitigation services, commercial radon, or a local contractor in Los Angeles County, use this page to separate the reading from the hiring decision. Confirm the result first, then open the local cost or quote path. Los Angeles County searchers are often looking for testing, mitigation services, or a commercial radon answer. The useful sequence is still the same: confirm the reading, then decide cost, credit, or quote.
Do not hire from a blind reading
A service search is only useful after the number is real. Use this page to verify the result band, open the cost path, and capture the quote signal if you talk to a contractor.
Service intent detected: testing, mitigation, or commercial radon searches need a result-to-cost path.
No reading yet means test first. 4.0+ means pricing and quote comparison become relevant.
Test result -> county cost path -> quote ledger if a contractor gives a number.
Measured Radon Data
Los Angeles County evidence before the next step
Los Angeles County, CA has more than the EPA map: CDC Tracking Network exposes 1,367 reported tests, 1.9 pCi/L county average, 0.7 pCi/L median, 9.5% of reported tests at or above 4.0 pCi/L, and 363.7 pCi/L high-end signal for 2008-2017.
Source window
2008-2017
County evidence type
Lower measured burden
County context only; your home test controls the decision.
Primary result
1.9 pCi/L
48th percentile in-state
4.0+ signal
9.5%
48th percentile in-state
High-end signal
363.7 pCi/L
98th percentile in-state
Official evidence dossier
Source record for Los Angeles County, CA
CDC Tracking provides comparable county-level measurement fields; state-specific sources still outrank it when they expose stable county tables.
Primary public source
National tracking data
Measurement window
2008-2017
Retrieved / checked
2026-05-05
County FIPS
06037
Evidence stack
County source
National tracking data
Primary source used for the county evidence row.
Federal map
EPA Map of Radon Zones
Zone 2 is context, not a property result.
Housing context
US Census ACS housing context
28.1% built before 1980; 3,599,561 housing units.
State follow-up
State radon program
Use the state source before hiring or interpreting local rules.
Primary field
1.9 pCi/L
Median field
0.7 pCi/L
4.0+ field
9.5%
Sample / volume
1,367 over 10 years
Metric shape
This is the most useful setup: county average, 4.0+ share, high-end readings, and 1,367 reported tests/properties can be read together instead of relying on one number.
Source limitation
CDC county summaries are based on national radon testing laboratories and participating state feeds; they are not a statistically designed survey of every home.
Property-level limit
Not a property-level diagnosis. The county record explains local evidence; your home's own test result controls the next decision.
County-specific interpretation
Los Angeles County looks lower at county level, but the home still needs its own number.
Los Angeles County is a home-specific check because 1.9 pCi/L average, 0.7 pCi/L median, and 9.5% of reported tests at or above 4.0. In-state rank: 48th percentile for average, and 48th percentile for 4.0+ share. The county signal is lower, but one house can still sit above the county pattern.
Real-estate use
Buyer or seller use: the county pattern is not enough for a credit demand by itself; use an actual home test to decide whether anything needs pricing.
Los Angeles County has a lower measured county signal, but the page should still push direct testing because individual homes can sit above the county pattern.
Use This EvidenceOfficial state path
Open the state radon program
Use state rules and local program contacts before choosing a contractor.
EPA hiring guidance
Find a qualified radon provider
EPA points homeowners to state programs and national proficiency listings.
Certified professional search
Search NRPP-certified pros
Use this after you have a valid result or need professional testing.
Lower-signal intent answer
Should homeowners in Los Angeles County still test for radon?
Los Angeles County has a lower county-level measured signal, but the page should still send homeowners to a direct test because individual homes can sit above the county pattern.
Enter the result. Pick the deal side. Get the route.
Service intent detected: testing, mitigation, or commercial radon searches need a result-to-cost path.
County signal
1.9 pCi/L
At or above 4.0
9.5%
Decision side
Foundation clue
Choose your next step
Start from the exact job, not another generic radon article.
Pick the situation that matches Los Angeles County, CA. Each route keeps the reading, deal side, or foundation clue attached so the next page answers the search instead of resetting the user.
Failed inspection
I need a repair or seller credit number
Open the local credit path with a 4.0+ buyer scenario already selected.
Open negotiation route4.0+ pCi/L
I have a high result and need the cost path
Go straight to the county estimate, quote context, and contractor checklist.
Open cost route2.0-3.9 pCi/L
I need to know if this number is bad
Use the level explanation first, then decide whether to retest, monitor, or price mitigation.
Open level routeNo test yet
I need the first valid result
Start with kit placement, timing, closed-house conditions, and result interpretation.
Open testing routePick the situation that matches you
You should not need to read the whole guide before clicking one of these. Start with the lane that matches your current stage, then come back for the deeper reference only if you still need it.
Use this as the pre-contractor triage for Los Angeles County: test first, price after 4.0+, and add any real quote to the ledger.
I have not tested yet
Do not price mitigation blind. Get the first number, then decide whether you need monitoring, quotes, or nothing at all.
My result is 2.0-3.9
Usually confirm the reading first. If it keeps showing up, use the county evidence and official guidance before deciding whether pricing makes sense.
My result is 4.0+
This is the EPA action line. Use the local cost page before calling contractors so you know the likely scope, timing, and budget.
I am buying or selling
Turn the reading into a credit or repair number before negotiation starts. This is the faster path than arguing from a generic article.
Already tested once and need the cleanest follow-up path?
Review retesting stepsLocal service next step
Looking for a service or cost answer?
Commercial radon searches usually need a different call than a one-family home: building type, testing protocol, occupancy, access, scope, and whether the quote is for testing, mitigation, or both. RadonVerdict is not a contractor directory. It turns the search into a decision: get or confirm the reading, open the local cost path after 4.0+, then record any real quote so the benchmark gets less generic.
Commercial provider search pack
Before contacting a commercial radon provider, write down building type, occupied areas, number of test locations, lowest occupied level, result band, deadline, and whether mitigation or testing documentation is the deliverable.
Provider lookup
Use the official state radon program and EPA provider guidance to verify licensing or certification before treating any local service listing as enough.
Local call script
I have a radon result of ___ pCi/L in Los Angeles County, CA. Before I compare quotes, can you confirm what foundation and suction method your price assumes, whether sump or crawl-space work is included, and how the post-mitigation retest will be documented?
Commercial and multifamily screen
Los Angeles commercial radon is not the same job as a single-family basement quote.
California's radon program points professionals to ANSI-AARST standards, including broader ground-contact testing for multifamily housing. For a Los Angeles apartment, office, school, warehouse, mixed-use, or retail property, ask for the testing protocol before you ask for a mitigation price.
1. Building profile
Count ground-contact units, occupied lower levels, slab/crawl areas, mechanical rooms, and tenant access limits.
2. Measurement plan
Confirm short-term versus long-term devices, duplicate/blank controls if applicable, and whether documentation is transaction-grade.
3. Mitigation scope
Separate testing-only, design-only, sub-slab suction, sub-membrane, fan, electrical, roofline, and post-mitigation retest costs.
4. Provider proof
Verify California approval or national certification before relying on a commercial quote page.
County Evidence Snapshot
Los Angeles County testing context
Los Angeles County is a moderate-signal county: the EPA map is useful context, but the local evidence, housing profile, and your own home test decide the next step.
EPA map signal
Zone 2
County-level predicted indoor screening range, not a home-level test result.
Housing base
3,599,561
100th percentile among 58 CA counties with data.
Older housing share
28.1%
7th percentile in-state; older homes often need clearer test placement decisions.
Median home value
$732,200
Used as context for whether mitigation is a small maintenance item or a negotiation issue.
Measured Radon Data
CDC Environmental Public Health Tracking Network Radon Tests from Labs
2008-2017
Average result
1.9 pCi/L
At or above 4.0
9.5%
Maximum reported
363.7 pCi/L
10-year tested
1,367
CDC county summaries are based on national radon testing laboratories and participating state feeds; they are not a statistically designed survey of every home.
County evidence interpretation
Lower measured burden
Primary result rank
48th percentile
1.9 pCi/L
4.0+ rank
48th percentile
9.5% at or above 4.0
High-end rank
98th percentile
363.7 pCi/L
Test volume rank
100th percentile
1,367 over 10 years
How to use this county data
Data source
National tracking data
CDC Tracking provides comparable county-level measurement fields; state-specific sources still outrank it when they expose stable county tables.
What the numbers show
Fuller county picture
This is the most useful setup: county average, 4.0+ share, high-end readings, and 1,367 reported tests/properties can be read together instead of relying on one number.
Nearby comparison
Nearby comparison: Closest counties by county average: Solano County (1.8 pCi/L) is just lower, and Monterey County (1.9 pCi/L) is just higher.
How this helps
Use this to understand why a lower county pattern still does not replace a direct home test.
What the data says
Los Angeles County, CA is measurement-backed for 2008-2017. The measured average is 1.9 pCi/L, and 9.5% of reported results are at or above 4.0 pCi/L. The high-end signal reaches 363.7 pCi/L.
Los Angeles County, CA sits at the 48th percentile for measured average, 48th percentile for 4.0+ share, 98th percentile for high-end readings, and 100th percentile for test volume among 58 measured counties in the state. Closest counties by county average: Solano County (1.8 pCi/L) is just lower, and Monterey County (1.9 pCi/L) is just higher.
What to do with it
Los Angeles County has a lower measured county signal, but the page should still push direct testing because individual homes can sit above the county pattern.
Retest trigger: a 2.0-3.9 pCi/L result can be watched or confirmed, while a 4.0+ result should still override the lower county pattern.
Source-backed context from CDC Tracking Network based on about 1,367 reported tests/properties plus comparable county-level measurement fields.
No reading yet
No reading yet: start with a test kit; the county data is context, not a substitute for the home result.
2.0-3.9 result
2.0-3.9 pCi/L: retest or monitor before paying for mitigation, then escalate if the level repeats or rises.
4.0+ result
4.0+ pCi/L: use the result for mitigation quotes, repair scope, or seller-credit negotiation; the county signal is no longer the deciding input.
Source hierarchy: CDC Tracking Network is used for this county, with EPA zone and Census housing data kept as supporting context. CDC Tracking provides comparable county-level measurement fields; state-specific sources still outrank it when they expose stable county tables.
Direct Answer
What radon risk level should homeowners assume in Los Angeles County?
Los Angeles County is currently categorized as EPA Zone 2 (Moderate Risk). Test all lived-in levels and confirm with follow-up testing if elevated.
| Evidence | Value |
|---|---|
| Area | Los Angeles County, CA |
| EPA Zone | Zone 2 |
| Primary Recommendation | Perform direct radon testing in the lowest livable level |
Your Radon Reading
Enter your home's measured level; the starting value is only a planning example until you have your own result.
Elevated - Consider Action
Your reading is below the US EPA action level (4.0 pCi/L), but this range still warrants follow-up testing. The World Health Organization uses 2.7 pCi/L as a tighter reference point.
If this was just a one-time snapshot, confirm it with another test or with longer tracking. If this level persists, planning mitigation is reasonable, especially for homes with frequent basement use, children, or pending real-estate transactions. Scroll down to see your estimated cost.
Understanding Radon Levels: Complete Reference
Below 2.0 pCi/L - Lower Concern, Keep Testing
Below both the EPA (4.0) and WHO (2.7) action reference levels. This usually means mitigation is not the next immediate step after a confirmed result. The average outdoor radon level is approximately 0.4 pCi/L, and there is no known risk-free indoor level. Periodic testing is still recommended because levels can change over time due to seasonal variations, changes in home ventilation, or foundation settling.
-4.0
2.0 - 4.0 pCi/L - Elevated, Consider Action
Exceeds the World Health Organization's reference level of 2.7 pCi/L but falls below the US EPA action threshold. The EPA states that homeowners should "consider fixing" homes in this range, especially if the home has a basement used as living space, if children are present, or in connection with a real estate transaction. Practical next step: run a confirmatory long-term test, then compare mitigation quotes if levels remain elevated.
-8.0
4.0 - 8.0 pCi/L - Action Recommended
Exceeds the EPA action level of 4.0 pCi/L. The EPA and Surgeon General strongly recommend mitigation within a few months. At this level, prioritize confirmatory testing and contractor planning. Standard sub-slab depressurization systems typically reduce indoor levels by 80-99%.
Above 8.0 pCi/L - Urgent Action Required
At these levels, the EPA recommends expedited mitigation - ideally within weeks, not months. Occupants should minimize time in lower-level rooms until the system is installed. Use a certified mitigator and request priority scheduling to shorten high-exposure time. Many mitigators offer priority scheduling for homes above 8.0 pCi/L.
Why Radon is Worth Monitoring in Los Angeles County
Los Angeles County falls in EPA Zone 2, where the predicted indoor screening range is between 2.0 and 4.0 pCi/L. Even when the countywide map signal sits below the EPA action level, geological variability means that some individual homes will still test above 4.0 pCi/L.
The soil composition in this area typically includes a mix of sedimentary formations that can contain moderate uranium deposits. Homes with basement or crawlspace foundations are particularly susceptible, as they provide more pathways for soil gas entry.
The World Health Organization recommends action at 2.7 pCi/L - well below the US EPA threshold. If you have children, spend significant time in below-grade rooms, or are buying/selling a home, testing is essential even in a Zone 2 area.
Radon & Health: What the Science Says
lung cancer
from radon
4.0 pCi/L
Radon is a Class A carcinogen - the same classification as asbestos and tobacco smoke. The National Academy of Sciences estimates that radon causes approximately 21,000 lung cancer deaths annually in the United States, making it the leading environmental cause of cancer death.
Unlike smoking, radon exposure is involuntary and often invisible. There is no safe level of radon - risk increases linearly with exposure. The good news: radon mitigation systems are highly effective, typically reducing indoor levels by 80-99% within hours of activation.
Source: US Environmental Protection Agency, "A Citizen's Guide to Radon" (EPA 402/K-12/002). National Academy of Sciences, Biological Effects of Ionizing Radiation (BEIR VI) Report, 1999.
Step 1: Test Your Home
Testing is the only way to know your home's radon level. Zone and county data tell you the regional signal, but your home could be significantly higher or lower than the countywide pattern. Start with a valid test setup before using any cost path.
State radon programs and EPA provider guidance are the right reference before hiring or confirming local requirements.
Open the state radon programAlready Know Your Level?
If your test shows 4.0 pCi/L or higher, get an itemized cost estimate specific to Los Angeles County - including regional labor rates and permit requirements.
Get Mitigation Cost Estimate ->CA Radon Regulations
California requires sellers to complete the Transfer Disclosure Statement (TDS), which covers known environmental hazards including radon.
California does not require specific radon licensing. Look for NRPP or AARST-certified professionals.
How to Test for Radon in Los Angeles County
Buy a Test Kit
Purchase a short-term charcoal test kit online or from a local hardware store. Cost: $15-$30. Place it in the lowest livable level of your home.
Wait 2-7 Days
Keep doors and windows closed (except normal entry/exit) during the test period. Avoid running whole-house fans. Mail the kit to the lab provided.
Read Your Results
If results are below 4.0 pCi/L, re-test every 2 years or use a monitor for ongoing tracking. If above 4.0, use our cost calculator to see mitigation options.
Related Radon Resources for Los Angeles County
Explore Other CA Counties
Official State Resource
California radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure rule tracked
California requires sellers to complete the Transfer Disclosure Statement (TDS), which covers known environmental hazards including radon.
Credential note
California does not require specific radon licensing. Look for NRPP or AARST-certified professionals.
Sources & Methodology
Radon zone classifications for Los Angeles County are sourced from the EPA's Map of Radon Zones, which uses geological surveys, indoor radon measurements, and soil permeability data to assign each county a risk tier.
Disclaimer: Zone data represents county-level screening ranges and cannot predict the radon level in any specific home. Testing is the only reliable method to determine your home's radon concentration. This content is for informational purposes and is not medical advice.
Content review: Source-level retrieval dates
Editorial and Data Transparency
- Author
- RadonVerdict Data Team (Public Data and Cost Modeling)
- Content Review
- Source-level dates shown below
- Data Retrieved At
- 2026-02-24
Primary Sources
- EPA Map of Radon Zones (retrieved 2026-02-21)
- EPA A Citizen's Guide to Radon (retrieved 2026-05-05)
- CDC Environmental Public Health Tracking - Radon Testing (retrieved 2026-05-05)
- Official CA radon program
- US Census Bureau, 2018-2022 American Community Survey 5-Year Estimates (retrieved 2026-02-24)