The house already has a radon mitigation system – do we need a radon test? - WNC Independent Labs
A radon test should be done every year or two to ensure that the mitigation system is still working properly.
They have mechanical motors and just like any motor they eventually wear out. We have also seen systems that were turned off or unplugged (usually because someone didn’t realize what it was).
31 January 2022 Radon Testing FAQ