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District reports nine short-term radon readings above action level; HVAC and sealing corrected most
Summary
At its March 2 meeting the Mankato Public School District presented its five-year radon testing report: 141 short-term kits were placed and nine readings initially exceeded 4 picocuries per liter; follow-up HVAC adjustments, a motor replacement and targeted sealing reduced levels on retest.
The Mankato Public School District presented its annual five-year radon report to the school board on March 2, 2026, reporting that short-term testing across district buildings found a small number of readings above the Minnesota action level of 4 picocuries per liter (pCi/L).
A facilities staff member told the board the district placed 141 short-term test kits across 121 locations from Nov. 10—Nov. 13. Nine initial readings returned above 4 pCi/L; the presenter said affected locations tended to be ground-level spaces or storage areas with direct contact to soil.
The district followed up with remediation testing and operational fixes. At one site identified as "Futures," staff said adjusting HVAC run schedules resolved the elevated readings on retest. At Jefferson a motor on a unit ventilator had failed; after maintenance and motor replacement the retest returned below 4 pCi/L. At Franklin the high results were concentrated in storage and rarely occupied spaces; the district plans crack sealing or installing targeted radon-mitigation systems where needed.
"Sometimes a schedule or a simple maintenance fix will address the spike," the facilities presenter said, describing a "crawl-walk-run" approach that starts with schedule changes before more expensive mitigation. The presenter added that some higher short-term readings appeared during unoccupied overnight hours and disappeared on a corrective retest.
District staff said they work with IEA (the district's health and safety consultant) to interpret results and determine next steps, including continuous-fan mitigation systems where sealing alone is unlikely to be sufficient. The presenter noted that short-term tests sample roughly a 72-hour window; when spikes occur during late-night hours, staff can pay for more detailed time-resolved testing to locate when concentrations peak.
Board members asked about the number of missed kits and protocol; the presenter said 5—10 kits are typically missed per year because devices are moved or located behind a closed door. The presenter emphasized the district will continue retesting after sealing or mechanical fixes and proceed to mitigation systems if necessary.
The board took no formal action on the radon report beyond receiving the information; staff said they will continue follow-up remediation testing and report back to the board as needed.
