Radon Testing

Radon Testing in Sioux Falls

A radon test is cheap, takes two days, and settles the question. Here's how testing works, which kind you need, and when the free kit from the state is the better call.

Why Test a Sioux Falls Home? The Map Says It Plainly

The EPA puts Minnehaha and Lincoln counties in Zone 1, its highest radon category. Tested homes in Minnehaha County average 6.5 pCi/L per the American Lung Association, well above the 4.0 federal action level.

But averages don't test your house. Two identical homes on the same street can read 2 and 12. The EPA's own guidance is blunt: no matter where you live, test. It's the only way to know your number.

Most South Dakota homes have never been tested. The American Lung Association counted roughly 16 tests per 1,000 housing units statewide over a decade. Testing puts you ahead of most of the Sioux Empire.

Testing Rules for a Sioux Empire Winter, or Any Season

A radon test is simple, but the conditions matter. Cut corners on conditions and you get a number you can't trust. A sealed-up house in heating season meets the closed-house rule almost by default; summer testing takes more discipline. Either way, a legitimate test means:

• The lowest livable level. Test the basement if anyone could regularly use it, finished or not. Not a closet, stairway, hallway, or crawlspace.
• Closed-house conditions. Windows shut, exterior doors used only for coming and going, starting 12 hours before a short-term test.
• 48 hours minimum. Every EPA-recognized radon test runs at least two full days. Anything shorter isn't a test.
• A written result. You get the number, the test conditions, and what the EPA says to do at that level.

Your Testing Options, Compared

Free state test kit

South Dakota DANR gives out 500 free test kits a year, lab analysis included. If one's available and you're not in a hurry, take it. We'd rather you test free than not test.

Hardware store kit

Under $20 and fine for a first look. Follow the closed-house rules, mail it promptly, and treat the result as a rough first read that a longer test can confirm.

Professional test

Cost guides put professional testing between $125 and $400 depending on equipment and turnaround. This is the right tool when a real estate deal needs a defensible number on a deadline, or when a DIY result came back confusing. Continuous monitors log hourly readings, so unusual swings while the seller controls the house stand out.

Consumer radon monitor

The $150–$300 desktop units are useful for watching trends, especially after a mitigation install. Expect the readings to bounce around day to day. Weather moves radon. Judge the long-term average, not this afternoon's spike.

Testing an office, daycare, or rental building instead? The same protocol applies, with more ground to cover. Start with commercial radon mitigation.

Testing When You're Buying or Selling Around the Sioux Falls Metro

Real estate is where testing gets urgent, because inspection windows are short. The EPA's transaction guidance fits a 48-hour test inside a normal inspection period, so a deadline is workable rather than scary.

• Buyers: ask for the seller's past results. Ask for a new test if the old one predates a renovation, skipped the basement, or is just old.
• Sellers: the EPA recommends testing before listing. A documented low number, or a mitigated house with a retest on file, is a selling point rather than a liability.
• Either side: who pays for mitigation is pure negotiation. A high test doesn't kill a deal. It usually just moves a thousand-and-change around the closing table.

Reading Your Result

One more local note: radon in water is mostly a private-well concern. Homes on city water can put that worry aside. The EPA estimates only 1 to 2 percent of airborne radon comes from household water. Soil gas under the foundation is the pathway that matters here.

Testing Questions People Call With

My test came back at 4.2. Is that bad?

It means: fix it, without alarm. The EPA action level is 4.0 pCi/L, so 4.2 is over the line where fixing is the official recommendation. It is not a number that makes your house dangerous to sleep in tonight. One caveat: radon moves with weather and seasons, so a 4.2 in July could be a 7 in January when the house is sealed up. A borderline result is a reason to mitigate or retest in heating season, not a reason to shrug.

What does the 4.0 "action level" actually mean? Is anything under it safe?

The 4.0 pCi/L action level is a policy threshold: the point where the EPA says fixing a home is clearly justified. Nothing about your lungs changes at 3.9. The same agency says no level is risk-free, recommends considering mitigation between 2 and 4, and notes outdoor air runs about 0.4 pCi/L. Modern systems get most homes below 2, so the practical question isn't "am I under 4" but "how low can this house reasonably get." We treat 4.0 as the minimum standard rather than the goal.

Do I really need to test here? The house next door tested fine.

Yes, and this is the one answer where geography does the arguing. Both Minnehaha and Lincoln counties are EPA Zone 1, the highest radon designation. The American Lung Association's data puts this county's tested homes at 6.5 pCi/L on average. For scale, even the LOWEST county average in South Dakota (Aurora County, at 4.9) tops the federal action level. House-to-house variation is huge, because radon follows soil pockets, foundation cracks, and how each house breathes; next-door neighbors routinely land on opposite sides of the line. Your neighbor's number is trivia. Yours is a $20 test away.

The house we're buying tested high. Should we walk away?

Not over radon alone. A high test is one of the most fixable findings an inspection can produce. It's a known problem with a standard fix, a cost that national guides put around $790 to $1,280, and a retest to prove the result. Even dramatic numbers like 12 or 20 pCi/L come down the same way. Treat it like a worn furnace: negotiate it, fix it, document it. The EPA's buyer guidance says the same thing in more federal language.

Tested High? Here's the Next Step

A high number isn't an emergency, and it isn't a mystery. It's a plumbing problem for air. See exactly what a fix involves and costs on our mitigation system installation page, or call and we'll walk through your result together.