Fans move surface moisture but leave elevated moisture content inside wood and subfloor for weeks. That trapped moisture continues to cause movement, cupping, crowning, buckling, and eventually produces mold in the subfloor cavity. Professional drying uses calibrated air movers, commercial dehumidifiers, and in hardwood situations, specialty systems that draw moisture out from within the boards. Daily readings confirm progress. Flooring refinished or reinstalled before moisture content reaches target levels will fail.