No mystery to it. Here is exactly what happens from the moment you call to the moment we hand the job back.
Establish the actual level with a proper test before anything is designed. Short-term test kits are inexpensive and widely available; results guide whether and how much mitigation is warranted.
Foundation and sub-slab conditions assessed, sometimes with a communication test that measures how far suction extends from a trial point. This sets the number of suction points.
Slab cored, pit excavated below, pipe set and sealed. Cracks, joints and penetrations sealed so the fan is not simply pulling conditioned air from the house.
Pipe run to the fan location outside conditioned space, then to a discharge above the roofline and away from windows. A manometer is fitted so system status is visible.
After the system has run for the specified period, a follow-up test confirms the reduction. Keep that result; it is the document a future buyer will ask for.
None of this is required — it just makes the visit quicker.