Final answer:
The minimum time a radon mitigation system should operate before post-mitigation testing is started is generally recommended to be at least 24 hours.
Step-by-step explanation:
The minimum time a radon mitigation system should operate before post-mitigation testing is started can vary depending on the specific circumstances. However, it is generally recommended that the system operates for at least 24 hours prior to testing. This allows enough time for the system to effectively reduce the radon levels in the building.