Class 8 Clean Room Requirementsby Wilhelm Schnotz
Clean rooms are specially built spaces maintained free of dust and other airborne particles as well as bacteria and other contaminants. They're used in research settings in the study of everything from biological specimens and particle experiments in physics to the construction of electronic components. Some uses require a greater degree of cleanliness, and the International Organization for Standardization, known commonly as the ISO, developed standards for clean-room classification. A Class 8 Clean Room is one of the lowest levels of clean-room environments, and has relatively lax standards of environmental control.
An ISO Class 8 clean room has the same stringency standards as a US FED STD 209E Class 100,000 clean room, and is about 100,000 times cleaner than natural air. Both measure the concentration of airborne particles in a cubic foot or air, and require fewer than 29,300 particles between 5 micrometers and 1 micrometer, 832,000 particles sized between 1 and 0.5 micrometers and fewer than 3.52 million particles smaller than 0.5 micrometer. For purposes of comparison, one inch is 25,400 micrometers.
A clean room must provide air circulation at all times. ISO standards require vents and filtration systems to cycle the entire volume of air in a clean room in a one-hour period. HEPA filters remove 99.97 percent of particles larger than 0.3 micrometers, and are required to keep circulated air free of contaminants. In addition to filtration systems, a clean room's circulation system must maintain a positive air pressure in relation to the outside environment so that air rushes out when the door is opened, blowing outside contaminants away from the room.
Construction and Outfitting
In order to keep contaminants from settling in a clean room, it must be constructed without surfaces where dust can collect. This includes building perfectly level floors, adding light fixtures that are sealed and smooth on the clean-room side and eliminating light switches and other fixtures. In addition, only stainless-steel or plastic workstations and furniture should be used; this prevents flaking of paint and dust created by the degradation of upholstery and foam cushions.
Clean Room Use
As with any level of clean room, anyone entering a clean room must wear a clean suit to trap dust and other contaminants that may be carried in on clothes and shoes into the room. Hair and exposed skin must be covered to keep biologically degraded contaminants at a minimum.
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