A semiconductor wafer processing system for polishing a substrate that generally includes a base having a first side and a second side, and at least one drive system that is disposed on the first side of the base. One or more polishing heads are coupled to the drive system for retaining a workpiece during polishing. A first enclosure is disposed on the first side of the base and defines a first volume that includes the drive system. A second enclosure is disposed on the second side of the base and defines a second volume. A first exhaust is coupled to the second volume. When the system is coupled to a facilities exhaust or other air handler, the first exhaust ventilates the second volume. In another aspect, a method for processing a substrate is also disclosed. Generally, the method includes the steps of monitoring the flow metrics of a first exhaust from a first enclosure and a second exhaust from a second enclosure. If the flow metrics fall outside a predetermined processing window, a step of polishing the substrate is stopped.