Introduction Datacom equipment center owners and operators focus much of their attention on the physical structure and performance of the datacom infrastructure environment (e.g.@ power@ cooling@ and raised-access floor equipment). However@ today's intricate and sensitive information technology (IT) equipment (also called datacom equipment or computer equipment throughout the book) requires a certain level of environmental control for gaseous and particulate contamination that is present within the facility's datacom equipment center environment. Datacom equipment center contamination is frequently overlooked and@ if left unrestrained@ can degrade the reliability and the continuous operation of mission-critical IT equipment within a facility. To maintain a high level of IT equipment dependability and availability@ it is critical to view contamination in a holistic way. It should be acknowledged that the datacom equipment center is a dynamic environment where many maintenance operations@ infrastructure upgrades@ and IT equipment change activities occur on a regular basis. Airborne contaminants harmful to sensitive electronic devices can be introduced into the operating environment in many ways during these and other activities. The fundamental focus areas that necessitate examination start with the outdoor ambient air pollutants surrounding the facility. Outdoor air that purposely enters the building for datacom equipment center free cooling@ datacom equipment center positive pressurization@ or human occupancy air changes must be filtered and possibly conditioned. Once inside the building@ maintenance operations within the building's environmental envelope and the datacom infrastructure equipment itself must be considered. Datacom workers also add contamination from hair@ lint on clothing@ and other contaminants tracked in on footwear to the datacom equipment center. With proper planning and controls@ datacom equipment center operators can minimize contamination and potential negative effects in the datacom equipment center. Datacom managers and operators should include a datacom equipment center environmental contamination section as part of the standard operating procedure. The association between contamination and hardware failures is often overlooked. Occasionally@ the absence of contamination controls results from cost-cutting actions or from lack of knowledge. Particle and gaseous contamination can result in intermittent equipment glitches or in unplanned shutdowns of critical systems that often mean significant business and financial losses. Examples of contamination events are provided throughout the book. In many cases@ the events are written generically to illustrate points that support the text. The intent of this publication is to provide basic information that is essential to the control and prevention of particulate and gaseous contamination within datacom facilities. Understanding the critical parameters outlined in this publication will provide equipment manufacturers and facilities operations personnel with a common set of guidelines for contamination control that can enhance the longevity of datacom equipment. The book does not cover issues related to contamination and filtration of open water systems@ such as condenser water systems@ used in datacom environments. ? The intended audience for this publication is: ? planners and datacom facility operation managers ? datacom facility architects and engineers who require insight on datacom environmental controls for gaseous@ organic@ and particulate contamination datacom facility service providers ? datacom equipment manufacturers