Airborne environmental cleanliness

IES (1992), Institute of Environmental Sciences, Federal Standard 209E, Airborne particulate cleanliness classes in cleanrooms and clean zones, Mount Prospect. Available at http //www.set3.com/papers/209e.pdf (accessed October 2006). 

Institute of environmental science and technology. In Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones Federal Standard U.S. Govt. Printing Office Washington, DC, 1992. 

All finishes should be selected to be resilient to expected average and worst-case environmental exposure such as high/low humidity or temperature, airborne contaminants, vibration, possible aggressive liquid spillages, cleanliness/hygiene requirements, etc. 

Areas for the manufacture of sterile products are classified according to the required characteristics of the environment. Each manufacturing operation requires an appropriate level of microbial and particulate cleanliness four grades (Table 22.1) are specified in the Rules and Guidance for Pharmaceutical Manufacturers and Distributors (1997), defined by measures of airborne contamination (Table 22.2). Environmental quality is substantially influenced by the air supplied to the manufacturing environment. 

These kinds of environmental contamination problems are everyday occurrences in the semiconductor industry because of the strict cleanliness demands required for the fabrication of silicon wafers and production of semiconductor devices. The purity of silicon wafers has a direct effect on the yield of devices, so it is crucial that trace element contamination levels are kept to a minimum in order to reduce defects. This means that any analytical methodology used to determine purity levels on the surface of silicon wafers, or in the high-purity chemicals used to mauufacture the devices, must use spotlessly clean instruments. These unique demauds of the semiconductor industry have led to the development of special air filtration systems that continually pump air through ultraclean high-efficiency particulate air (HEPA) filters to remove the majority of airborne particulates. 

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