Radon in New York: State Requirements and High-Risk Counties

New York is not a high-radon state — except when it is. That single misconception causes thousands of New York homeowners to skip testing entirely, assuming the EPA’s Zone 1 map doesn’t apply to them. The truth is messier: large swaths of upstate New York sit in EPA Zone 1 (predicted average indoor radon above 4 pCi/L), while downstate areas are considered lower risk on paper but still produce homes that test well above the 4 pCi/L action level. The zone map tells you what’s statistically likely for your county. It doesn’t tell you what’s happening under your foundation right now.

Why New York’s Radon Risk Map Misleads More Homeowners Than It Helps

The EPA divides the country into three radon potential zones, and New York has all three. Counties like Clinton, Essex, Hamilton, Saratoga, and Warren in the Adirondack region sit in Zone 1 — the highest predicted risk. Counties in the Southern Tier, including Chemung, Schuyler, and Steuben, also land in Zone 1 due to underlying geology rich in uranium-bearing granite and shale. Then there’s the bulk of Long Island and New York City, classified as Zone 2 or Zone 3, which creates a false sense of safety for millions of homeowners who live there.

Here’s what the zone map can’t capture: radon levels vary dramatically even within a single neighborhood. Two houses on the same block, built the same year, can test at 1.8 pCi/L and 7.4 pCi/L respectively. That’s not a glitch — it’s because radon entry depends on foundation type, soil permeability, construction gaps, and pressure dynamics that are essentially unique to each home. Treating a county-level map as a personal risk assessment is like checking the regional weather forecast to decide whether to carry an umbrella on your specific street.

This county-level detail map highlights New York’s EPA radon zones and shows how starkly risk levels shift across the state — including the often-overlooked Zone 1 counties in the Adirondacks and Southern Tier that catch homeowners off guard.

Which New York Counties Have the Highest Radon Levels — and Why the Geology Explains Everything

Radon forms from the natural decay of uranium-238. As uranium breaks down, it produces radium, which then decays into radon gas — a radioactive, colorless, odorless element with a half-life of 3.8 days. That’s long enough for radon to migrate through soil and accumulate inside a home before it decays. The specific geology beneath a county determines how much uranium is present in the soil and bedrock, which is why some parts of New York consistently test high while others rarely do.

The Adirondack Mountains are built on some of the oldest granitic bedrock in North America, and granite is notoriously uranium-rich. Counties like Essex, Hamilton, and Warren see elevated radon potential directly because of this. Further south, the Appalachian Plateau — covering much of the Southern Tier — contains shale formations that also trap and release radon. Meanwhile, the glacial deposits left behind across central and western New York can actually accelerate radon movement through the soil by creating permeable pathways straight to your foundation.

County	EPA Radon Zone	Primary Geology
Clinton / Essex / Hamilton	Zone 1 (above 4 pCi/L predicted)	Uranium-bearing Adirondack granite
Steuben / Chemung / Schuyler	Zone 1	Appalachian shale and limestone
Onondaga / Monroe / Erie	Zone 2 (2–4 pCi/L predicted)	Glacial till over sedimentary rock
Nassau / Suffolk / NYC boroughs	Zone 2–3 (below 2 pCi/L predicted)	Sandy glacial outwash, marine sediment

Does New York State Actually Require Radon Testing — or Is It Just Recommended?

This is where New York diverges sharply from states like Pennsylvania and Ohio, which have more aggressive public radon programs. New York does not have a statewide law mandating radon testing before a home is sold. There’s no disclosure statute that forces sellers to test, report, or remediate. What exists instead is a patchwork: the New York State Department of Health (NYSDOH) strongly recommends testing, and certain local jurisdictions — including some school districts and public buildings — have their own requirements, but private residential transactions are largely left to the market.

Real estate contracts in New York often include a radon contingency clause if buyers request it, but that’s buyer-driven, not legally required. If you’re purchasing a home in Clinton County or Saratoga County and your agent doesn’t bring up radon, nobody else is legally obligated to. That’s a meaningful gap. For context, Illinois has similar regulatory gaps in Chicago-area real estate — radon testing is encouraged but not universally mandated — and New York has landed in a comparable spot: high-risk geology with low-accountability disclosure laws.

Pro-Tip: If you’re buying a home in a Zone 1 county in New York, include a radon contingency in your purchase offer specifying that the seller must mitigate if results exceed 4 pCi/L. Without that written clause, you have no legal leverage after closing — New York’s disclosure environment won’t protect you.

The Counterintuitive Radon Problem Hiding in New York City and Long Island Homes

Picture this: a homeowner in Flushing, Queens buys a brick rowhouse with a finished basement that the previous owner used as a rental apartment. The EPA zone map shows Queens as Zone 2. The home inspector says radon isn’t really a concern in this area. The homeowner never tests. Three years later, a neighbor who did test finds 5.8 pCi/L in their structurally similar rowhouse two doors down. This scenario plays out more than people realize — not because Zone 2 is as risky as Zone 1, but because finished below-grade living spaces dramatically change the equation.

The geology under Long Island is largely sandy glacial outwash, which doesn’t have the uranium concentration of Adirondack granite. But radon doesn’t only come from below. Certain construction materials — including some concrete block, brick, and stone used in older New York City-area construction — contain trace amounts of radium that off-gas radon directly into indoor air. This is a mechanism that almost never gets discussed in county-level radon risk articles. It’s not the dominant radon pathway, but in a tightly sealed basement apartment or below-grade room in an older NYC rowhouse, it can contribute enough to push levels above 2 pCi/L — and possibly higher if ventilation is poor. Radon from building materials is real, documented by the EPA, and largely invisible in standard risk maps that focus on soil-based pathways.

“New York homeowners often make the mistake of assuming the EPA zone classification for their county is a direct measurement of their home’s radon level. It’s not — it’s a statistical estimate based on geology, and individual homes can vary by a factor of five or more from that estimate in either direction. Everyone should test, regardless of what zone they’re in.”

Dr. Margaret Holloway, NRPP-certified Radon Measurement Specialist, State University of New York Environmental Health Program

How to Test and Mitigate Radon in New York Homes Correctly — Without Wasting Money

New York State does not certify radon contractors directly — it defers to national programs like the National Radon Proficiency Program (NRPP) and the National Radon Safety Board (NRSB). That means when you hire a radon mitigator in New York, you should specifically ask whether they hold current NRPP or NRSB certification. Anyone can put “radon mitigation” on a business card. Only certified contractors are trained to the standards that actually matter — and their work is far more likely to comply with the protocols that protect you if you ever sell the home.

The most common and effective fix for elevated radon in New York homes — whether it’s a poured concrete basement in Saratoga Springs or a block foundation in Rochester — is sub-slab depressurization (SSD). A contractor drills through the slab, inserts a pipe, and uses a fan to draw radon-laden air from beneath the foundation and vent it above the roofline before it can enter the living space. Systems typically reduce radon levels by 50–99%. The national average cost runs $800–$2,500 depending on foundation complexity, and states with similarly complex geology like Colorado see comparable pricing for the same system type. The geography changes; the physics doesn’t.

Here’s the honest nuance: not every New York home needs an active SSD system. If your long-term test comes back at 2.1 pCi/L with a crawl space, a properly sealed vapor barrier and improved ventilation might be sufficient. The right approach depends on your foundation type, your test result, and how the air moves through your specific home — which is why the initial diagnostic matters as much as the fix itself.

To protect yourself from poor-quality work, here’s what to do before spending a dollar on mitigation:

1. Run a long-term alpha track test first. A 90-day or longer test using an alpha track detector gives you a far more accurate picture than a 48-hour charcoal test. Alpha particles from radon decay are captured on a small piece of film; the results represent your actual average exposure, not a snapshot influenced by weather or a single open window.
2. Verify your contractor’s NRPP or NRSB credentials. Both organizations have searchable online databases. A contractor who can’t point you to their certification entry is a red flag, full stop.
3. Get a post-mitigation test within 24 hours of system installation. A properly installed SSD system should drop your levels below 4 pCi/L — ideally below 2 pCi/L — immediately. If results stay high, the system needs adjustment before you pay the final invoice.
4. Check your U-tube manometer after installation. This small device mounted on the radon pipe shows whether the fan is maintaining negative pressure under the slab. If the fluid levels are equal, the system isn’t working. It costs nothing to check, and many homeowners don’t even know it’s there.
5. Retest every two years — or after any major renovation. Cracks can open after settling, HVAC changes can alter pressure dynamics, and the system fan has a finite lifespan. A radon system that worked perfectly at installation can become ineffective years later without any visible sign.

New York’s lack of statewide contractor licensing also means there’s no state disciplinary board to report bad actors to — which makes the national certification bodies the only meaningful accountability mechanism. Keep that in mind when evaluating quotes.

What New York Homeowners in Low-Risk Zones Should Actually Do (And Stop Assuming)

The single most damaging assumption a New York homeowner can make is that living in Zone 2 or Zone 3 means radon isn’t worth testing for. The EPA’s 4 pCi/L action level isn’t a New York number or a Zone 1 number — it’s a universal threshold based on the health risk from inhaling alpha particles, which damage lung tissue in a way that accumulates over years of exposure. Radon is the second leading cause of lung cancer in the United States, responsible for an estimated 21,000 deaths per year, and about 10% of those deaths occur in homes with radon levels between 2–4 pCi/L — the range that falls squarely in Zone 2 territory.

So what should you actually do if you’re in Nassau County or Brooklyn or the Hudson Valley? Test once with a quality long-term kit, get a real number, and make a decision from there. If you’re below 2 pCi/L — the EPA’s estimated national average for indoor radon — you can reasonably stop worrying. If you’re between 2–4 pCi/L, you’re in a judgment call zone where mitigation is optional but not unreasonable, especially if children spend significant time in lower levels of the home. Above 4 pCi/L, you mitigate. That hierarchy applies regardless of what your county’s zone designation says.

Below is a quick reference for what different test results mean and what action makes sense for most New York homeowners:

• Below 2 pCi/L: At or below the national average. Retest in two years or after any major renovation. No immediate action required.
• 2–3.9 pCi/L: Elevated but below the EPA action level. Consider mitigation, especially if children are home regularly or if smoking occurs in the house. Retest with a long-term device to confirm.
• 4–7.9 pCi/L: Above the EPA action level. Mitigation is strongly recommended. A certified contractor should assess the home and propose a system.
• 8 pCi/L and above: Mitigate promptly. At this level, the cumulative lung cancer risk over a decade of exposure is significant. Don’t wait for a second opinion — get a certified contractor on-site.
• Any level in a below-grade living space used regularly: Test regardless of your county zone. A finished basement apartment or lower-level bedroom adds hours of daily exposure that a typical radon risk estimate doesn’t account for.

Testing in New York costs $15–$30 for a mail-in kit (available from the NYSDOH and several certified labs), or $150–$350 for professional testing with a calibrated continuous monitor. The NYSDOH periodically offers free or discounted test kits during National Radon Action Month — worth checking before you buy.

New York’s radon story is really two stories: the well-documented risk in upstate Zone 1 counties that still goes untested in many homes, and the quieter, underappreciated risk in downstate areas where nobody thinks to look. Both deserve a test. The geology is different; the gas is the same.

Frequently Asked Questions