Radon shows up in Johnson County real estate constantly, and for a predictable reason: the county averages 5.3 pCi/L against the EPA’s 4.0 pCi/L action level, and the whole county is EPA Zone 1. An elevated result during an inspection period is a routine event here, not a deal-breaking surprise.
What makes transaction testing different from homeowner testing is that the number has to hold up to scrutiny from someone with money on the line.
Why continuous monitors, not kits
For a home sale, use a continuous radon monitor placed by a certified professional. It logs a reading every hour for 48 hours and produces a report showing the whole curve.
That hourly record is the point. It shows whether a window was opened on day two, whether the HVAC was cycling oddly, whether the readings are stable or spiking. A mailed-in charcoal kit produces a single averaged number with no way to audit the conditions — fine for your own information, weak as a negotiating document.
What Kansas actually requires
Kansas does not require a radon test to sell a house. There is no statutory disclosure trigger tied to a radon measurement. Testing happens because a buyer asks for it during the inspection period.
What Kansas does require is that any radon test performed for hire be conducted by a professional holding current KDHE certification, under the Kansas Radon Certification Law effective 2011. A test run by an uncertified party is not just weak evidence — commissioning it as a paid service violates state law.
Statute K.S.A. 48-16a10 also requires certified testers to report results to the state quarterly.
Test conditions that make a result defensible
- Closed-house conditions for at least 12 hours before and throughout the test.
- Lowest lived-in level — a basement counts if it is finished or could reasonably be occupied.
- Away from exterior walls, drafts, and HVAC vents, at normal breathing height.
- Not in a kitchen, bathroom, or laundry, where humidity skews readings.
If those conditions were not maintained, expect the other side to challenge the number, and expect them to be right to.
Timing around a closing
Inspection periods are short. A 48-hour test plus lab-free instrument readout means results the same week, but the placement has to be scheduled early in the period, not on its last day. Call as soon as the inspection window opens.
If the result is elevated and mitigation gets negotiated, a standard single-foundation system is typically a one-day install, and a post-mitigation verification test should be part of the agreement. Do not accept “system installed” as the closing condition. Accept “system installed and verified below 4.0.”
If you are the seller
Testing before you list is worth considering. An elevated result you already fixed, with a post-mitigation test in hand, is a non-issue at inspection. The same result discovered by the buyer’s inspector is a negotiation.
Certification
Ask for the KDHE certification number of whoever tests your home. Verify it with the KDHE Radon Program at 785-296-1560 or kdhe.radon@ks.gov.
Want a straight answer about your house? We will tell you whether an $8–15 test kit is enough before we quote anything.
Call (913) 555-0147Common questions
Is a radon test required to sell a house in Kansas?
Kansas does not require a radon test to sell a home. Testing is negotiated between buyer and seller and is commonly requested during the inspection period. Kansas does require that radon testing performed for hire be done by a KDHE-certified professional.
Who pays for radon mitigation in a home sale?
It is negotiated, not fixed by law. In Johnson County it is common for a buyer to request mitigation as an inspection repair and for the seller to credit or complete it before closing. Because a typical system is a low four-figure cost, it usually settles without derailing a deal.