Radon is a naturally occurring gas produced by the breakdown of uranium in soil and rock, and it can seep into homes through foundation cracks, sump pits, and gaps around pipes entering the basement or lowest level. It has no smell, no color and no taste, which means the only way to know whether a home has an elevated radon level is to test for it — you cannot detect it by any of your senses, and levels vary from house to house even on the same street depending on soil conditions and how the specific foundation was built.
There are two general testing approaches. Short-term tests (commonly run over a period of a few days) give a quicker read and are common in real-estate transactions where time is limited; long-term tests (commonly run over 90 days or more) give a more representative picture of a home's average radon level across seasonal variation, since radon levels can fluctuate. The EPA publishes guidance on both testing approaches and on what level of radon warrants mitigation — we follow that guidance rather than asserting our own threshold.
Testing itself is straightforward and non-invasive: a device (either a passive short-term kit sent to a lab, or a continuous monitor) is placed in the lowest livable level of the home under closed-house conditions, left in place for the test duration, and then either analysed by a lab or read directly. If a result comes back elevated, the next step is radon mitigation (a separate service, typically a sub-slab depressurization system) — testing tells you the level, mitigation is what reduces it.
Signs you have a radon testing problem
- You're buying or selling a home and radon testing is part of the transaction or requested by the buyer
- You've never tested your current home for radon, or it's been several years since the last test
- You have a finished basement or spend significant time in the lowest level of the home
- A neighbouring property or your general area has previously tested with elevated radon
- You want a long-term test to understand your home's actual average radon exposure across seasons
Why Manhattan sees this
Radon risk is generally driven by underlying soil and geology rather than building age or style, so a brand-new NYC-metro home and a century-old one can each test either high or low — it genuinely depends on the specific lot and foundation, which is exactly why testing (not assumption) is the only reliable approach.
In real-estate transactions across the NYC metro, radon testing is commonly bundled into the same inspection contingency period as a general home inspection, so we work to the same transaction timeline where that's the reason for the test.
Finished basements — common across NYC-metro homes with additional living space below grade — are exactly the space EPA guidance points to for lowest-level testing, since that's where radon concentration is typically highest in a home.