Cleanrooms are contamination-free environments where high-tech manufacturing and assembly take place.  Cleanrooms range from very small chambers, called microenvironments, to large-scale rooms, called ballrooms.  Cleanroom technology is used in a wide range of industries including semiconductor assembly, biotechnology, pharmaceutical, aerospace, food, medical devices and hospitals.  There are a number of important aspects to consider while determining which cleanroom type fits the needed application.  This includes the cleanliness class, fabrication type, and special features such as ESD control, pass throughs, and a gowning area. Cleanliness class is a standard determined by the contamination control industry.  They currently use a government specification known as Federal Standard 209D to provide a qualified and standardized method for measuring how clean the air is in a cleanroom. Six classes have been established to designate cleanroom cleanliness.