Professional radon testing is the only way to know whether your Cincinnati home is safe. Because radon is colorless and odorless, you cannot detect it without specialized equipment — and because levels vary dramatically by season, foundation type, and house construction, even neighbors can have wildly different results.
In the Cincinnati metro, where Hamilton, Butler, Warren, and the Northern Kentucky counties are all in EPA Radon Zone 1, testing is essentially mandatory before any real estate transaction and strongly recommended for every long-term homeowner.
Short-term vs. long-term radon testing
The EPA recognizes two main testing protocols:
Short-term testing (48 to 96 hours)
The most common professional approach. A continuous radon monitor (CRM) or charcoal canister is placed in the lowest livable level of the home for 2 to 4 days under closed-house conditions. Lab analysis or instrument readout provides an average radon concentration in pCi/L. Used for real estate transactions and initial screening.
Long-term testing (90 days to 1 year)
Alpha track detectors are deployed for longer periods to capture seasonal variation. Provides a more accurate annual average and is recommended when initial short-term tests are borderline (2.0-4.0 pCi/L) or when you want certainty before deciding on mitigation.
What happens during a professional radon test
For real estate or homeowner testing, a continuous radon monitor (CRM) is the gold standard:
- The CRM is placed in the lowest livable area of the home — typically a finished basement, or the main level if there's no usable basement
- It's set 20+ inches off the floor, away from windows, exterior doors, and HVAC vents
- Closed-house conditions begin 12 hours before the test and continue through the entire test period (windows and doors closed except for normal entry/exit)
- The monitor records hourly readings for 48 to 96 hours
- Results are downloaded and a report is generated showing both the average concentration and hour-by-hour variation
Understanding your radon test results
The EPA Action Levels
Above 4.0 pCi/L: The EPA strongly recommends mitigation. This is the regulatory threshold.
2.0 - 4.0 pCi/L: The EPA advises considering mitigation. Many homeowners — especially those with small children or smokers in the household — choose to mitigate at this level.
Below 2.0 pCi/L: Generally considered acceptable, though no level of radon exposure is risk-free.
A good way to contextualize these numbers: the EPA estimates that living in a home at 4.0 pCi/L is comparable to the lung cancer risk of smoking eight cigarettes per day, or getting 200 chest X-rays per year. At 20 pCi/L, the risk is roughly equivalent to smoking two and a half packs a day.
When should you test for radon?
- Before purchasing a home — almost always required in inspection contingencies
- Before listing a home — to avoid mid-transaction surprises
- After mitigation system installation — to confirm system performance
- Every two years — for general homeowner peace of mind
- After major foundation work — basement waterproofing, foundation crack repair, or significant landscape changes around the home
- If you've never tested — even if you've owned the home for years
Radon testing for real estate transactions
In Cincinnati's real estate market, radon testing is included in roughly 80% of home inspection contracts. The test is usually performed by a licensed home inspector or radon professional and takes place during the standard 10-14 day inspection window.
If results come back above 4.0 pCi/L, buyers typically request that the seller mitigate before closing — or credit the buyer the mitigation cost (usually $900-$1,600) at closing. We work to closing-deadline timelines and can usually install within 5-7 business days. Read more on our real estate transactions page.
DIY testing vs. professional testing
Short-answer charcoal canister kits sold at hardware stores ($15-$30) provide reasonable preliminary screening but have known limitations: they're sensitive to humidity, can be tampered with, and don't provide hour-by-hour data. They are not accepted for real estate transactions in most cases. For peace-of-mind screening, they're acceptable. For anything binding, use a professional with a calibrated continuous radon monitor.