Borderline radon in Columbus: what to do at 2, 3 or 5 pCi/L

Your radon report came back with a number between 2 and 8 pCi/L, and nothing on it says whether that means shrug or schedule. This guide sorts the answer by result band, using EPA's own risk figures, the testing strategy Ohio writes into its measurement rules, and the parts of the call that only your household can make.

Two EPA lines frame every result

EPA's action level is 4 pCi/L: at or above it, the agency's advice is to fix the house. Below that, EPA still recommends considering a fix anywhere from 2 to 4 pCi/L. For scale, the average American home sits around 1.3 pCi/L indoors, and outdoor air runs about 0.4.

The reason for a second, softer line is that lung cancer risk does not switch on at 4. It climbs steadily with the concentration, all the way down the scale. The action level is a line drawn for policy, not a threshold of safety, so a 3.6 and a 4.1 are much closer to each other in risk than either one is to a 1.3. That is why each band below spends as much attention on how trustworthy your number is as on which side of 4 it lands. If the units or the report layout are unclear, start with what a radon result means.

Under 4 pCi/L: no required action, but 2 to 4 earns a closer look

Ohio's strategy for a house that is not changing hands lives in Addendum A of the state radon measurement protocol (appendix A to OAC 3701-69-07). It treats a first short-term result under 4 as needing no action, with a retest in two years or after a renovation. EPA layers its nuance on top: in the 2 to 4 range, a fix is worth considering.

So what does considering look like at 2.5 or 3? EPA's lifetime risk table is the most useful tool here. Among 1,000 people who never smoked, lifetime exposure at 2 pCi/L corresponds to about 4 radon lung cancers; at 4 pCi/L, about 7. Among 1,000 smokers, the same two levels correspond to about 32 and about 62. A smoker living at 2 pCi/L carries roughly the lifetime risk EPA assigns a never smoker at 20 pCi/L (about 32 versus about 36 per 1,000).

For a never-smoking household with a result in the low 2s, a two-year retest is a reasonable plan. For a result near 3.5, or any household with a smoker, a long-term test is a stronger next move, because it replaces a few days of air with the average over months. The long-term test FAQ explains how that works for results in this band.

4 to under 8 pCi/L: confirm first, then decide on the average

Is 5 pCi/L bad? It is above EPA's action level, so it is a number to act on. What Ohio's protocol does not ask is that you act on one short test in this band. It offers two routes: a second short-term test, or a long-term test that captures the year-round average. Then the decision rests on the average.

Put the follow-up device exactly where the first one sat, because Ohio's protocol never averages results taken in different locations. A second reading from the same basement room, averaged with the first, gives a number you can stand on. A second reading from an upstairs bedroom answers a different question and cannot be blended with the first.

At 5 pCi/L you sit just above EPA's 4 pCi/L row (about 7 per 1,000 never smokers, about 62 per 1,000 smokers) and well below the 8 pCi/L row (about 15 and about 120). If the average confirms 4 or higher, the usual fix is an active sub-slab system, which runs $1,200 to $2,400 for a typical Central Ohio basement or slab house according to our pricing guide.

8 pCi/L and up: one more short test, then act

Here Ohio's strategy calls for a second short-term test rather than a long-term one, and a decision on the average of the two. The practical logic is time. A long-term device has to run past 90 days to count as long-term, and at these concentrations each extra month is spent at the steep end of EPA's table. At 8 pCi/L or higher, the second test exists to confirm the number, not to talk you out of it.

Results in this range are not rare around Columbus. The American Lung Association's 2022 Ohio report, using CDC tracking data for 2008 through 2017, put Franklin County's estimated mean pre-mitigation result at 9.5 pCi/L across more than 16,000 tests, the most of any county in the state.

Why a summer result deserves a second look

This matters most for results logged in June, July and August. A short-term test only knows the few days it ran. In a Columbus summer, those days bring a small temperature gap between the house and the outdoors, sometimes a reversed one while the air conditioning runs, so the stack effect that draws soil gas into a heated house is weak. Ohio's protocol also requires a closed house for any test under 96 hours, and that is a harder promise to keep when the windows have been open all week and the whole-house fan is part of the evening routine.

A summer reading under 4 is thinner reassurance than the same number from January or from a long-term test, and a summer reading over 4 is no reason to wait. Some houses do run the other way, reading higher in warm months, which is one more reason a single short test from any season is a shaky basis for a borderline call. The short-term versus long-term comparison lays out when each kind of test fits.

Household factors that tip a borderline call

The EPA table already shows the biggest factor, smoking. After that, the question is simply who spends hours at the level that was tested:

• Someone sleeps downstairs. A basement bedroom, a teenager's den over a crawl space, or a guest suite in a walkout puts every night at the tested level.
• Someone works downstairs. A home office in a finished Dublin or Hilliard lower level turns the working day into lower-level hours.
• The space is about to change. A basement finish planned for next year is a reason to settle the question now, before walls and ceilings close off easy pipe routes.
• Nobody uses the space. A basement that holds only the furnace and holiday boxes still feeds air to the floors above, so an empty lower level lowers the stakes of a borderline number without erasing them.

The same 3.5 pCi/L means something different in a house where nobody goes downstairs than in one where a smoker sleeps down there. If you want a second set of eyes on your number, walk through the radon diagnosis page, or call or text us with the report in hand and we will help you choose between a follow-up test and a fix.