After fixing your home's radon problem, it's important to retest to make sure the mitigation system is working properly. You should wait at least 24 hours after the repair is done, then place the test kit in the same lowest livable area. I'd also recommend testing during the heating season when windows are closed. The process is just like the first test, but now it's about confirming safety, not finding the problem. radon retest after repair 8