Cleanroom

A cleanroom is an environment, typically used in manufacturing or scientific research, that has a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapors. More accurately, a cleanroom has a controlled level of contamination that is specified by the number of particles per cubic meter at a specified particle size. To give a perspective, the ambient air outside in a typical urban environment might contain as many as 35,000,000 particles per cubic meter, 0.5 μm and larger in diameter, corresponding to an ISO class 9 cleanroom.
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A software development approach aimed at producing software with the minimum number of errors.
(1994-12-12)

a room combining the use of air filters and continuous air circulation to produce levels of air borne particles that are lower, and typically much lower than normal atmospheric dust levels. Outdoor atmospheric dust levels are on the order of 400,000 particles/ft3 >0.5µm in size. Cleanroom cleanliness levels generally are agreed to begin at 100,000 particles/ft3 and extend down to 0.01 particles/ft3 or less! See also, Cleanroom Class.