Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
Locations and reports
Radon Levels in Seminole County, Florida
EPA puts Seminole County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 1.6% of 190 (2023) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
1.6%
16.9 pts below FL
- Seminole
- 1.6%
- Florida
- 18.5%
190 tests, 2023
Median result
0.6pCi/L
Below action level
- Seminole
- 0.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
190
15th of 30 by tests
- Seminole
- 190
- Broward
- 2,165
Reported to CDC before any fix, 2023
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in Florida
19 of 30
Middle half
- Seminole
- 1.6%
- Marion
- 44.5%
By share, of 30 with 30+ tests
Read a result for Seminole County
Starts at Seminole County's median, 0.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.6 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Seminole County's median reported result, 2023.
The data
Seminole County, At a glance
Seminole County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Seminole County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 2.7% |
| 2015 | 3.7% |
| 2016 | 1.0% |
| 2017 | 6.7% |
| 2018 | 1.9% |
| 2019 | 5.6% |
| 2020 | 0.0% |
| 2021 | 0.5% |
| 2022 | 0.0% |
| 2023 | 1.6% |
2023: 1.6%. Across these years the share ran from 0.0% to 6.7%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 190 tests reported to CDC for Seminole County over 2023, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Seminole County, Compared
Seminole County radon figures, compared
Calculated by Radon411Only 3 of 190 radon tests reported for Seminole County in 2023 reached 4 pCi/L (1.6%). The median result, 0.6 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 13.3 pCi/L.
Across 49 Florida counties pooled together, 18.5% of tests reached that level, so Seminole County runs 16.9 points below its state. Against the national pool of 33.4%, the gap is 31.8 points lower. Its place in the state: 19th of 30 Florida counties with 30 or more tests for the same period.
Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 1.6% share point the same way here. Of 4 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 0.0% (Brevard County) to 9.5% (Orange County).
Below the action level, 168 tests (88.4%) came in under 2 pCi/L, against 57.3% statewide, and 19 tests (10.0%) fell between 2 and 4, against 24.2% statewide. Over 10 years of annual figures the share held within 2 points, from 2.7% in 2014 to 1.6% in 2023; its peak was 6.7% in 2017. USGS geology rates 100% of the county's land low radon potential.
The busiest year on file was 2021, with 432 tests reported; the quietest, 2020, had 98.
Seminole CountyFlorida, pooled
1.6% % of tests18.5% % of tests
| Year | Tests | Seminole County, at or above 4 pCi/L | Florida, pooled |
|---|---|---|---|
| 2014 | 184 | 2.7% | 25.7% |
| 2015 | 136 | 3.7% | 26.5% |
| 2016 | 100 | 1.0% | 24.3% |
| 2017 | 105 | 6.7% | 21.7% |
| 2018 | 162 | 1.9% | 23.5% |
| 2019 | 196 | 5.6% | 29.6% |
| 2020 | 98 | 0.0% | 23.2% |
| 2021 | 432 | 0.5% | 15.4% |
| 2022 | 402 | 0.0% | 22.8% |
| 2023 | 190 | 1.6% | 18.5% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Seminole County, Geology
The ground under Seminole County
PredictedUSGS's geologic map puts all of Seminole County's mapped land in one class: low radon potential. All of it lies in the area the map calls Gulf/Atlantic Lowland and Central Highland, to which USGS gives a radon index of 6, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Gulf/Atlantic Lowland and Central Highland | sand, silt, clay, gravel | Low | 6 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Seminole County beside the ground around it
Across Florida 7.1% of the land is rated moderate; none of Seminole County's is. None of the 4 counties that border it has any moderate-potential ground either.
The map rates the ground, not the air in any home.
Local help
Seminole County, Local resources
Radon testing and mitigation in Seminole County
- Florida’s Radon ProgramFlorida’s Radon Program, run by Florida Department of Health, licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Florida.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Protect your family by requesting a FREE radon test kit.
- Compare kits
- Professionals in Florida77 professionals are listed in Florida.
What Florida's program says
- Phone
- 850-245-4288
- PHtoxicology@FLhealth.gov
- Licensing of radon professionals
Florida Statutes require the certification of businesses and individuals providing radon services or any other radon related activity.
What it means
Seminole County, Questions
Questions about radon in Seminole County
Are radon levels high in Seminole County?
In 2023, 1.6% of the radon tests reported to CDC for Seminole County, Florida were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.6 pCi/L. Of 30 Florida counties with 30 or more tests for the same period, 18 reported a higher share; pooled, the state comes to 18.5%.
Which counties border Seminole County?
Seminole County borders 4 counties: Orange County, Volusia County, Lake County and Brevard County.
Products
Seminole County, Products
Testing a home in Seminole County
In Seminole County, 1.6% of 190 tests reported to CDC in 2023 reached 4 pCi/L, against 18.5% pooled across Florida. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Seminole County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
MonitorX-Sense
XR0A-SR battery digital radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Seminole County, Bordering counties
Counties bordering Seminole County
Calculated by Radon411- Radon levels in Orange CountyEPA zone 3
9.5%at or above 4 pCi/L
Median 0.9 pCi/L · 1,107 tests · 7.9 points above Seminole County
- Radon levels in Volusia CountyEPA zone 3
1.2%at or above 4 pCi/L
Median 0.6 pCi/L · 163 tests · 0.4 points below Seminole County
- Radon levels in Lake CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.6 pCi/L · 159 tests · 1.6 points below Seminole County
- Radon levels in Brevard CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.7 pCi/L · 205 tests · 1.6 points below Seminole County
Seminole County, Cities and towns
Cities and towns in Seminole County
The Census Bureau estimates 491,884 residents in Seminole County for July 1, 2025, 20,413 more than in 2020 (+4.3%). Packed into its land, that is 1,590 people per square mile. No town dominates: Sanford, the largest, has 67,483 residents, 13.7% of the total. Together its 7 incorporated places hold 53.3% of those residents; the other 46.7% live outside any of them. Reported testing is thin here: 190 tests over 2023, or 0.4 for every 1,000 residents (2025 estimate), where Florida as a whole comes to 0.7.
From Sanford to Lake Mary, CDC publishes no figure by town: each reads Seminole County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Sanford | 67,483 | +10.3% | 13.7% |
| Altamonte Springs | 48,000 | +4.0% | 9.8% |
| Oviedo | 41,317 | +3.4% | 8.4% |
| Winter Springs | 39,585 | +3.1% | 8.0% |
| Casselberry | 31,872 | +9.6% | 6.5% |
| Longwood | 16,892 | +9.5% | 3.4% |
| Lake Mary | 16,789 | −0.3% | 3.4% |
7 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Seminole County, Homes
Homes in Seminole County
Of Seminole County's 197,167 homes, 62% are detached houses, against 55% across Florida; 22% are in buildings of five or more homes. Half of its homes were built before 1988, close to Florida's 1988: 6% date from before 1960 and 27% from 2000 or later. 66% of occupied homes are lived in by their owner (Florida: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Seminole County | Florida |
|---|---|---|
| Housing units | 197,167 | 10,082,356 |
| Detached houses | 62% | 55% |
| In buildings of 5 or more | 22% | 25% |
| Mobile homes | 2% | 8% |
| Built before 1960 | 6% | 10% |
| Built since 2000 | 27% | 30% |
| Middle year built | 1988 | 1988 |
| Owner-occupied | 66% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.