Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Ontario County, New York
EPA puts Ontario County in Zone 1, its highest radon zone, and only 7 radon tests from it are on file with CDC (2023). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
32.8%
8.3 pts above NY
- Ontario
- 32.8%
- New York
- 24.5%
1,448 tests, 2008 to 2017
Median result
2.6pCi/L
Below action level
- Ontario
- 2.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
1,448
20th of 61 by tests
- Ontario
- 1,448
- Erie
- 13,822
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in New York
20 of 61
Middle half
- Ontario
- 32.8%
- Chemung
- 52.3%
By share, of 61 with 30+ tests
Read a result for Ontario County
Starts at Ontario County's median, 2.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.6 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Ontario County's median reported result, 2008 to 2017.
The data
Ontario County, At a glance
Ontario County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Ontario County in
USGS geologic potential: High across 82% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Ontario County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 38.1% |
| 2015 | 16.7% |
| 2016 | 5.3% |
| 2017 | 38.9% |
| 2018 | 20.0% |
| 2019 | 42.3% |
| 2020 | 15.4% |
| 2021 | 40.0% |
| 2023 | 28.6% |
2023: 28.6%. Across these years the share ran from 5.3% to 42.3%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 7 tests were reported to CDC for Ontario County over 2023, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Ontario County, Compared
Ontario County radon figures, compared
Calculated by Radon411In Ontario County, about 3 in 10 reported tests over the 2008 to 2017 laboratory totals (475 of 1,448) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 2.9 points lower. Across 62 New York counties pooled together, 24.5% of tests reached that level, so Ontario County runs 8.3 points above its state.
The newest figure, in 2023, counts only 7 tests (28.6% at or above 4 pCi/L), too few to compare, so this reading uses the 1,448-test figure.
Of 6 neighbours with a figure, 3 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 15.1% (Monroe County) to 45.9% (Yates County). By share, Ontario County is 20th of 61 New York counties with 30 or more tests for the same period.
Half the tests came in under 2.6 pCi/L and half over it; the single highest reached 114.5 pCi/L. Below the action level, 544 tests (37.6%) came in under 2 pCi/L, against 51.7% statewide, and 429 tests (29.6%) fell between 2 and 4, against 23.7% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 32.8% share point the same way here. USGS geology rates 82% of the county's land high radon potential. CDC also counts 73 tests taken after mitigation in Ontario County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2019, with 26 tests reported; the quietest, 2021, had 5.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Ontario County, State data
New York's own radon test data
MeasuredWhat New York's own agencies publish about radon tests in Ontario County, with their period. These are not CDC's figures and are never added to them.
MeasuredState figures, not CDC's
What the New York State Department of Health reports for Ontario County
Indoor air radon testing data (Environmental Public Health Tracker): short-term charcoal canister tests requested through the NYSDOH Radon Program, presented as five-year rolling averages. Period: 2015-2019. The publisher also lists 15 earlier periods.
Share at or above 4 pCi/L
26.7%
Average result
4.1 pCi/L
Tests behind these figures
21 tests a year on average
- Every figure is a five-year rolling average: the average result is the rolling average of each year's mean, and the test count is an average per year.
- The data only include tests requested through the NYSDOH Radon Program, and therefore may not capture all radon tests performed in a county.
- The data include both screening tests and post-mitigation tests, as it is not always possible to tell them apart.
- Radon testing by homeowners is optional in New York, so the values may not be representative of every home in the county.
- These figures describe tests reported to the New York State Department of Health in this area. They count a different set of tests than CDC's figures and are not a reading of any one home.
Measured: New York State Department of Health data, 2015-2019.
Ontario County, Geology
The ground under Ontario County
PredictedMost of the ground under Ontario County is one class on USGS's geologic map: 82.2% of its land is high radon potential, with 17.8% moderate. The map puts 82.2% of Ontario County in the area it calls Allegheny Plateau and 17.8% in Erie-Ontario Lowland. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Allegheny Plateau | Shale, limestone, and sandstone. | High | 12 | 82.2% |
| Erie-Ontario Lowland | Limestone, dolomite, shale, sandstone, and salt deposits. | Moderate | 9 | 17.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Ontario County beside the ground around it
Ontario County has more high-potential ground than New York as a whole: 82.2% of its land against 48.9%. Of the 6 counties that border it, 3 have more high-potential ground, Yates County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Ontario County, Local resources
Radon testing and mitigation in Ontario County
- Radon ProgramRadon Program, run by New York State Department of Health, does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in New York.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Providing patients with information about how low-cost test kits may be obtained from the Radon Program.
- Compare kits
- Professionals in New York88 professionals are listed in New York.
What New York's program says
- Phone
- 518-402-7556
- radon@health.ny.gov
- Licensing of radon professionals
NYS does not certify or license radon testers.
What it means
Ontario County, Questions
Questions about radon in Ontario County
Are radon levels high in Ontario County?
In 2023, 28.6% of the radon tests reported to CDC for Ontario County, New York were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.2 pCi/L. Of 61 New York counties with 30 or more tests for the same period, 19 reported a higher share; pooled, the state comes to 24.5%.
Which counties border Ontario County?
Ontario County borders 6 counties: Yates County, Seneca County, Livingston County, Wayne County, Monroe County and Steuben County.
Products
Ontario County, Products
Testing a home in Ontario County
In Ontario County, 32.8% of 1,448 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 24.5% pooled across New York. In Zone 1 the year-round level in Ontario County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
MonitorPYZYCKYH
RD17 plug-in radon detector with a rechargeable battery and color screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Ontario County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Ontario County
Explore
Ontario County, Bordering counties
Counties bordering Ontario County
Calculated by Radon411- Radon levels in Yates CountyEPA zone 1
45.9%at or above 4 pCi/L
Median 3.5 pCi/L · 135 tests · 13.1 points above Ontario County
- Radon levels in Steuben CountyEPA zone 1
45.3%at or above 4 pCi/L
Median 3.4 pCi/L · 1,080 tests · 12.5 points above Ontario County
- Radon levels in Livingston CountyEPA zone 1
38.3%at or above 4 pCi/L
Median 3.1 pCi/L · 519 tests · 5.5 points above Ontario County
- Radon levels in Wayne CountyEPA zone 2
26.9%at or above 4 pCi/L
Median 2.0 pCi/L · 793 tests · 5.9 points below Ontario County
- Radon levels in Seneca CountyEPA zone 1
21.3%at or above 4 pCi/L
Median 2.0 pCi/L · 319 tests · 11.5 points below Ontario County
- Radon levels in Monroe CountyEPA zone 2
15.1%at or above 4 pCi/L
Median 1.8 pCi/L · 7,113 tests · 17.7 points below Ontario County
Ontario County, Cities and towns
Cities and towns in Ontario County
The Census Bureau estimates 113,130 residents in Ontario County for July 1, 2025, 663 more than in 2020 (+0.6%). That works out to 176 people per square mile of land. Geneva, the largest place on its list (12,552 residents in all), extends beyond Ontario County, so no share of the total is worked out for it. Testing is reported here more often than across the state: CDC's 1,448 reported tests for 2008 to 2017 come to 12.8 for every 1,000 residents (2025 estimate), against 4.9 for New York.
From Geneva to Rushville, CDC publishes no figure by town: each reads Ontario County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Genevaextends beyond Ontario County | 12,552 | −2.0% | Counted whole |
| Canandaigua | 10,347 | −0.5% | 9.1% |
| Victor | 2,906 | +6.6% | 2.6% |
| Clifton Springs | 2,170 | −1.5% | 1.9% |
| Phelps | 1,850 | −1.2% | 1.6% |
| Manchester | 1,628 | −1.9% | 1.4% |
| Shortsville | 1,358 | −2.4% | 1.2% |
| Bloomfield | 1,326 | −2.1% | 1.2% |
| Naples | 945 | −3.6% | 0.8% |
| Rushvilleextends beyond Ontario County | 688 | +0.4% | Counted whole |
10 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 Ontario County is counted whole, so it has no share.
Ontario County, Homes
Homes in Ontario County
Of Ontario County's 53,001 homes, 66% are detached houses, against 41% across New York; 11% are in buildings of five or more homes. Much of Ontario County is recent building: 21% of its homes have gone up since 2000 and the middle year built is 1975, against 1958 for New York. 73% of occupied homes are lived in by their owner (New York: 54%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Ontario County | New York |
|---|---|---|
| Housing units | 53,001 | 8,539,536 |
| Detached houses | 66% | 41% |
| In buildings of 5 or more | 11% | 34% |
| Mobile homes | 7% | 2% |
| Built before 1960 | 36% | 53% |
| Built since 2000 | 21% | 12% |
| Middle year built | 1975 | 1958 |
| Owner-occupied | 73% | 54% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.