For many of us, our direct experience with the reality of a semiconductor fabrication facility is limited to meeting rooms, cleanrooms and analytical laboratories. These facilities are, however, part of much more complex structures that contain an intricate infrastructure of ancillary environments housing regulatory, production and delivery systems for the different services and utilities needed for day-to-day fab operation. Figure 1 is a layout diagram for a typical semiconductor fab that shows the ancillary areas needed to provide utility services to the cleanroom production zone. These services include ultrapure water, bulk high purity gases such as nitrogen and argon, exhaust gas handling and disposal, and cleanroom air systems. This section discusses these fab utility systems and supplies context for how different products in MKS's portfolio are employed in these areas. Also, while many of the references in this section are to 200 mm wafer processing, the subject matter is generally applicable to 300 mm wafer processing as well.