Radon Levels, EPA Zone & Basement Testing in Fairfax, VA
Short answer for homeowners, buyers, and sellers: Fairfax is a strong county-level radon signal. You still need a home test, but this is not a county where skipping the first test makes sense.
Do not guess in a higher-risk county
Most users should either get a first test or move a 4.0+ result straight into mitigation pricing.
Higher countywide chance of 4.0+ readings.
2.0-3.9 pCi/L usually means retest or track. 4.0+ is where EPA action and quote planning start to matter.
No reading: test now. Reading at 4.0+: move into mitigation planning.
Measured Radon Data
Fairfax evidence before the next step
Fairfax, VA has more than the EPA map: Virginia Department of Health exposes 261 reported tests, 3.2 pCi/L county average, and 33.6 pCi/L high-end signal for 2016-2024.
Source window
2016-2024
County evidence type
Elevated measured burden
County context only; your home test controls the decision.
Primary result
3.2 pCi/L
31st percentile in-state
4.0+ signal
Not available
n/a in-state
High-end signal
33.6 pCi/L
54th percentile in-state
Official evidence dossier
Source record for Fairfax, VA
Virginia values come from VDH-received 2016-2024 indoor air radon results by locality. VDH suppresses averages below 25 tests, so test count and maximum can remain useful even when the average is unavailable.
Primary public source
Official county measurements
Measurement window
2016-2024
Retrieved / checked
2026-05-06
County FIPS
51600
Evidence stack
County source
Official county measurements
Primary source used for the county evidence row.
Federal map
EPA Map of Radon Zones
Zone 1 is context, not a property result.
Housing context
US Census ACS housing context
31.0% built before 1980; 9,323 housing units.
State follow-up
State radon program
Use the state source before hiring or interpreting local rules.
Primary field
3.2 pCi/L
Median field
Not available
4.0+ field
Not available
Sample / volume
261 reported tests
Metric shape
This source gives a directional county average. Pair it with a fresh home test before mitigation or credit decisions.
Source limitation
VDH says the map displays indoor air radon results received by its Radon Program from 2016-2024, using voluntary reports from five major radon test-kit vendors and professional testers after removing duplicates, post-mitigation tests, inappropriate locations, upper-floor tests, and incomplete addresses. VDH suppresses locality averages when fewer than 25 tests are available. RadonVerdict normalized the rendered VDH Tableau table because Tableau Public summary data, crosstab, and workbook export are permission-denied.
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
Fairfax is elevated enough that map-reading should turn into a home test.
Fairfax is a priority-test case because 3.2 pCi/L average. In-state rank: 31st percentile for average. The county signal is strong enough to justify testing or retesting before cost decisions.
Real-estate use
Buyer or seller use: ask for a fresh lowest-level test before inspection deadlines, tie any 4.0+ result to a contractor quote, and do not negotiate from the county signal alone.
Fairfax has enough measured elevation that buyers and owners should not stop at the county signal; confirm the home and price mitigation if the result crosses 4.0.
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.
Elevated-intent answer
Are radon levels elevated in Fairfax?
Fairfax has enough measured elevation that the answer should not stop at the EPA zone. 3.2 pCi/L primary measured result, and 33.6 pCi/L high-end signal makes a first test or confirmatory retest the right next step before cost decisions.
Pick 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.
Jump into a prefilled Fairfax action plan based on the result you already have, instead of starting from a generic cost page.
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 stepsCounty Evidence Snapshot
Fairfax testing context
Fairfax is a higher-priority testing county because the EPA zone signal is high and the page now ties that signal to local housing context.
EPA map signal
Zone 1
County-level predicted indoor screening range, not a home-level test result.
Housing base
9,323
40th percentile among 133 VA counties with data.
Older housing share
31.0%
12th percentile in-state; older homes often need clearer test placement decisions.
Median home value
$649,600
Used as context for whether mitigation is a small maintenance item or a negotiation issue.
Measured Radon Data
Virginia Department of Health Radon Testing Results
2016-2024
Average result
3.2 pCi/L
At or above 4.0
Not available
Maximum reported
33.6 pCi/L
Reported tests
261
VDH says the map displays indoor air radon results received by its Radon Program from 2016-2024, using voluntary reports from five major radon test-kit vendors and professional testers after removing duplicates, post-mitigation tests, inappropriate locations, upper-floor tests, and incomplete addresses. VDH suppresses locality averages when fewer than 25 tests are available. RadonVerdict normalized the rendered VDH Tableau table because Tableau Public summary data, crosstab, and workbook export are permission-denied.
County evidence interpretation
Elevated measured burden
Primary result rank
31st percentile
3.2 pCi/L
4.0+ rank
n/a
Not available at or above 4.0
High-end rank
54th percentile
33.6 pCi/L
Test volume rank
77th percentile
261 reported tests
How to use this county data
Data source
Official county measurements
Virginia values come from VDH-received 2016-2024 indoor air radon results by locality. VDH suppresses averages below 25 tests, so test count and maximum can remain useful even when the average is unavailable.
What the numbers show
Average result only
This source gives a directional county average. Pair it with a fresh home test before mitigation or credit decisions.
Nearby comparison
Nearby comparison: Closest counties by county average: Henrico County (3.1 pCi/L) is just lower, and Caroline County (3.3 pCi/L) is just higher.
How this helps
Use this to decide whether the county signal is strong enough to justify testing or retesting before cost decisions.
What the data says
Fairfax, VA is measurement-backed for 2016-2024. The measured average is 3.2 pCi/L. The high-end signal reaches 33.6 pCi/L.
Fairfax, VA sits at the 31st percentile for measured average, n/a for 4.0+ share, 54th percentile for high-end readings, and 77th percentile for test volume among 134 measured counties in the state. Closest counties by county average: Henrico County (3.1 pCi/L) is just lower, and Caroline County (3.3 pCi/L) is just higher.
What to do with it
Fairfax has enough measured elevation that buyers and owners should not stop at the county signal; confirm the home and price mitigation if the result crosses 4.0.
Retest trigger: a 2.0-3.9 pCi/L home result should be confirmed here because 3.2 pCi/L average keeps the county from being a dismiss-it signal.
Source-backed context from Virginia Department of Health based on about 261 reported tests/properties plus comparable county-level measurement fields.
No reading yet
No reading yet: run a short-term test now, then confirm or price mitigation quickly if the result is elevated.
2.0-3.9 result
2.0-3.9 pCi/L: retest or track longer-term rather than dismissing the result, because the county distribution has meaningful elevated readings.
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: Virginia Department of Health is used for this county, with EPA zone and Census housing data kept as supporting context. Virginia values come from VDH-received 2016-2024 indoor air radon results by locality. VDH suppresses averages below 25 tests, so test count and maximum can remain useful even when the average is unavailable.
Direct Answer
What radon risk level should homeowners assume in Fairfax?
Fairfax is currently categorized as EPA Zone 1 (High Risk). Prioritize testing now and prepare for possible mitigation.
| Evidence | Value |
|---|---|
| Area | Fairfax, VA |
| EPA Zone | Zone 1 |
| 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.
Warning: Action Required - EPA Threshold Exceeded
At 5.5 pCi/L, this reading is above the EPA action level. Prompt mitigation planning is recommended after confirmatory testing.
Typical mitigation systems reduce radon by 80-99%. See your itemized cost estimate below.
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 a Serious Concern in Fairfax
Fairfax sits in a geological region with elevated uranium concentrations in the underlying bedrock and soil. As uranium naturally decays, it produces radium, which further decays into radon gas. This gas migrates upward through soil and enters homes through foundation cracks, gaps around pipes, and sump pits.
In Zone 1 counties like Fairfax, the EPA predicts indoor screening levels are commonly above 4.0 pCi/L. Individual homes can still vary dramatically - even neighboring houses can differ by a factor of 10 or more. This is why every home needs its own test, regardless of what a neighbor's reading shows.
Factors that amplify radon entry include: basement foundations (more soil contact area), granitic or shale bedrock, tight energy-efficient construction (less natural ventilation), and negative indoor air pressure from HVAC systems, exhaust fans, and dryers.
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 Fairfax - including regional labor rates and permit requirements.
Get Mitigation Cost Estimate ->VA Radon Regulations
Virginia requires sellers to complete a Residential Property Disclosure Statement covering known defects and environmental hazards including radon.
Virginia does not require specific radon licensing. NRPP or AARST certification is recommended.
How to Test for Radon in Fairfax
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 Fairfax
Explore Other VA Counties
Official State Resource
Virginia 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
Virginia requires sellers to complete a Residential Property Disclosure Statement covering known defects and environmental hazards including radon.
Credential note
Virginia does not require specific radon licensing. NRPP or AARST certification is recommended.
Sources & Methodology
Radon zone classifications for Fairfax 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)
- Virginia Department of Health Radon Testing Results (retrieved 2026-05-06)
- Official VA radon program
- US Census Bureau, 2018-2022 American Community Survey 5-Year Estimates (retrieved 2026-02-24)