Heating-season radon testing in Greater Cincinnati, done right

The furnace is running again across Greater Cincinnati and the storm windows are down, which makes the next five months the most revealing time of year to measure radon. A closed house behaves the way it will all winter, and a test run now shows you the air your family actually breathes from Thanksgiving to spring break.

Why the heating season gives the clearest reading

Warm indoor air rises and slips out through the attic, recessed lights, and upper-floor gaps. The house replaces it by drawing air in low, and the lowest openings are the ones touching soil: the joint where the basement floor meets the wall, the sump, plumbing holes cut through the slab. That pull is at its strongest when it is cold outside and warm inside, so a heating-season test catches the house when soil gas has the easiest path in.

There is a practical reason too. Ohio's radon measurement protocol requires closed-building conditions to begin at least 12 hours before any test shorter than 96 hours. In July that means asking everyone to stop opening windows. In November the house is already living that way.

A short-term test in the heating season is a snapshot of your home under the conditions that concentrate radon, not a year-round average. If you want the annual picture, EPA points to a long-term test of more than 90 days, and a kit started in October will be finished well before the spring thaw.

Pick the room before you open the package

The Ohio protocol and EPA's Citizen's Guide agree on the basics. Test the lowest level of the home that is used, or could be used, as living space, in a room people actually spend time in: a family room, den, playroom, or bedroom. Skip kitchens, bathrooms, laundry rooms, closets, crawl spaces, and anywhere near the sump, because readings taken there are not supposed to drive a decision either way.

Many basements in this region hold the washer, the furnace, and a finished rec room on the same slab. Put the kit in the rec room end, not beside the dryer. If the basement is unfinished storage today but you plan to finish it or sell the house, test down there anyway, since that is the space a buyer's inspector will measure.

Split-levels, which turn up across the postwar suburbs from Anderson Township to Colerain, deserve a note of their own. The Ohio protocol has professionals test each foundation type separately: the basement, a room over the crawl space, and a room on the slab. A single kit in the family room can miss the level that reads highest.

A placement checklist you can do with a tape measure

These distances come from the placement rules Ohio-licensed testers follow, and they work just as well for a kit you place yourself:

• 20 inches to 6 feet above the floor
• at least 3 feet from exterior doors, windows, and supply or return vents, and out of any direct airflow
• at least 1 foot from exterior walls
• at least 4 inches clear of other objects around and above the device
• at least 4 feet from furnaces, fireplaces, space heaters, and direct sunlight
• at least 10 feet from a sump pit

On a level larger than 2,000 square feet, licensed testers add a second device. For a homeowner screening test, one well-placed kit is a reasonable start, and a second kit at the far end of a sprawling ranch costs little.

What quietly ruins a test

Most bad results are not lab errors. They come from the house not being held closed, or from the device sitting in moving air. During the test and the 12 hours before it:

• keep windows and exterior doors shut, except for normal coming and going
• let the furnace run normally, and leave any radon system fan on
• do not run a whole-house fan or burn the fireplace unless it is your main heat source
• keep ceiling fans, portable dehumidifiers, humidifiers, air purifiers, and window units at least 20 feet from the kit
• use bath fans, range hoods, and the dryer only as briefly as you normally would

Weather matters as well. The Ohio protocol bars short tests during severe storms or sustained winds of 30 mph or more, because a blustery front can briefly change the pressure around a house. Late autumn cold fronts through the Ohio Valley can bring exactly that, so glance at the forecast and start the kit on a calm stretch. Houseguests matter too: a week of relatives propping the back door open for the dog is a week of dilution.

Where to get a kit on either side of the river

Ohio homeowners can order a free test kit through the Ohio Department of Health program at ohio.radon.com. In Northern Kentucky, a hardware-store kit works the same way, and anyone testing for pay must be certified under Kentucky law (KRS 309.436). Hardware stores sell charcoal kits as well; follow the exposure time on the package exactly and mail it back the same day it comes down.

If the test is for a home sale, it has to be run by someone licensed for it. In Ohio, testing radon for someone else requires an ODH radon tester or mitigation specialist license under ORC 3723.02, and Kentucky requires certified measurement contractors. Our radon testing page covers the professional options.

Reading the result and deciding what comes next

EPA's action level is 4.0 pCi/L, and it recommends considering a fix between 2.0 and 4.0. EPA's testing steps for a homeowner are simple. Under 4.0, no immediate action, though testing again in the future is wise. At 4.0 or higher, run a follow-up test, either a second short-term kit or a long-term one. If the first result is more than twice the action level, run the second short-term test right away rather than waiting months.

For context on what your neighbors see, Ohio Department of Health data from licensed professionals since 2010 shows about 22 percent of Hamilton County tests above 4.0, and roughly 36 to 37 percent in Butler, Warren, and Clermont counties. Our radon levels by ZIP code table breaks those results down further. A ZIP average still cannot tell you your own number; only the kit can.

Start the test on a calm week, leave it alone, and send it back promptly. If the result lands at 4.0 or above, or between 2.0 and 4.0 with someone sleeping on the lowest floor, call or text us and we will walk through the follow-up. The diagnosis tool is a good first stop if you are not sure what your result means, and our testing frequency answer covers when to test again.