Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in St. Johns County, Florida
EPA puts St. Johns County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 0.0% of 96 (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
0.0%
18.5 pts below FL
- St. Johns
- 0.0%
- Florida
- 18.5%
96 tests, 2023
Median result
0.7pCi/L
Below action level
- St. Johns
- 0.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
96
23rd of 30 by tests
- St. Johns
- 96
- 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
23 of 30
Middle half
- St. Johns
- 0.0%
- Marion
- 44.5%
By share, of 30 with 30+ tests
Read a result for St. Johns County
Starts at St. Johns County's median, 0.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.7 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. St. Johns County's median reported result, 2023.
The data
St. Johns County, At a glance
St. Johns County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 96% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for St. Johns County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 0.0% |
| 2015 | 0.0% |
| 2016 | 0.0% |
| 2017 | 11.1% |
| 2018 | 0.0% |
| 2019 | 0.0% |
| 2020 | 0.0% |
| 2021 | 0.0% |
| 2022 | 0.0% |
| 2023 | 0.0% |
2023: 0.0%. Across these years the share ran from 0.0% to 11.1%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 96 tests reported to CDC for St. Johns 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).
St. Johns County, Compared
St. Johns County radon figures, compared
Calculated by Radon411Only 0 of 96 radon tests reported for St. Johns County in 2023 reached 4 pCi/L (0.0%). The median result, 0.7 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 3.3 pCi/L.
Across 49 Florida counties pooled together, 18.5% of tests reached that level, so St. Johns County runs 18.5 points below its state. Against the national pool of 33.4%, the gap is 33.4 points lower. Its place in the state: 23rd 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 0.0% share point the same way here. Of 2 neighbours with a figure, all 2 reported a larger share at or above 4 pCi/L; the spread is 0.0% (Clay County) to 6.2% (Duval County).
Below the action level, 89 tests (92.7%) came in under 2 pCi/L, against 57.3% statewide, and 7 tests (7.3%) fell between 2 and 4, against 24.2% statewide. Over 6 years of annual figures the share held within 2 points, from 0.0% in 2014 to 0.0% in 2023; its peak was 0.0% in 2014. USGS geology rates 96% of the county's land low radon potential.
The busiest year on file was 2023, with 96 tests reported; the quietest, 2020, had 7.
St. Johns CountyFlorida, pooled
0.0% % of tests18.5% % of tests
| Year | Tests | St. Johns County, at or above 4 pCi/L | Florida, pooled |
|---|---|---|---|
| 2014 | 57 | 0.0% | 25.7% |
| 2015 | 33 | 0.0% | 26.5% |
| 2018 | 73 | 0.0% | 23.5% |
| 2021 | 46 | 0.0% | 15.4% |
| 2022 | 54 | 0.0% | 22.8% |
| 2023 | 96 | 0.0% | 18.5% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
St. Johns County, Geology
The ground under St. Johns County
PredictedUSGS's geologic map puts all of St. Johns County's mapped land in one class: low radon potential. 96.4% 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 | 96.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
St. Johns County beside the ground around it
Across Florida 7.1% of the land is rated moderate; none of St. Johns 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
St. Johns County, Local resources
Radon testing and mitigation in St. Johns 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
St. Johns County, Questions
Questions about radon in St. Johns County
Are radon levels high in St. Johns County?
In 2023, 0.0% of the radon tests reported to CDC for St. Johns County, Florida were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.7 pCi/L. Of 30 Florida counties with 30 or more tests for the same period, 22 reported a higher share; pooled, the state comes to 18.5%.
Which counties border St. Johns County?
St. Johns County borders 4 counties: Clay County, Duval County, Putnam County and Flagler County.
Products
St. Johns County, Products
Testing a home in St. Johns County
In St. Johns County, 0.0% of 96 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 St. Johns County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Monitor
Wave Plus battery radon and air quality monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- App only
Method: Alpha spectrometry
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
St. Johns County, Bordering counties
Counties bordering St. Johns County
Calculated by Radon411- Radon levels in Flagler CountyEPA zone 3
100.0%at or above 4 pCi/L
Median 6.4 pCi/L · 2 tests · 100.0 points above St. Johns County
- Radon levels in Duval CountyEPA zone 3
6.2%at or above 4 pCi/L
Median 0.4 pCi/L · 792 tests · 6.2 points above St. Johns County
- Radon levels in Clay CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.0 pCi/L · 36 tests · 0.0 points above St. Johns County
- Radon levels in Putnam CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.9 pCi/L · 10 tests · 0.0 points above St. Johns County
St. Johns County, Cities and towns
Cities and towns in St. Johns County
St. Johns County is growing: the Census Bureau puts it at 346,328 residents on July 1, 2025, up 25.0% from 277,119 in 2020. That works out to 577 people per square mile of land. No town dominates: St. Augustine, the largest, has 16,141 residents, 4.7% of the total. Reported testing is thin here: 96 tests over 2023, or 0.3 for every 1,000 residents (2025 estimate), where Florida as a whole comes to 0.7.
From St. Augustine to Marineland, CDC publishes no figure by town: each reads St. Johns County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| St. Augustine | 16,141 | +9.8% | 4.7% |
| St. Augustine Beach | 6,810 | −0.4% | 2.0% |
| Marinelandextends beyond St. Johns County | 9 | +12.5% | Counted whole |
3 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). A place that extends beyond St. Johns County is counted whole, so it has no share.
St. Johns County, Homes
Homes in St. Johns County
Of St. Johns County's 127,144 homes, 72% are detached houses, against 55% across Florida; 13% are in buildings of five or more homes. Much of St. Johns County is recent building: 56% of its homes have gone up since 2000 and the middle year built is 2002, against 1988 for Florida. Owners live in 82% of the occupied homes (Florida: 67%), so for most households a test and a fix are their own to order.
| Homes | St. Johns County | Florida |
|---|---|---|
| Housing units | 127,144 | 10,082,356 |
| Detached houses | 72% | 55% |
| In buildings of 5 or more | 13% | 25% |
| Mobile homes | 5% | 8% |
| Built before 1960 | 5% | 10% |
| Built since 2000 | 56% | 30% |
| Middle year built | 2002 | 1988 |
| Owner-occupied | 82% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.