A cleanroom is a controlled environment with a specialized design for controlling variables such as 1) the density of airborne particles per cubic meter, or 2) the temperature of the room. Cleanrooms are essential for manufacturing processes which require high degrees of cleanliness or a precise temperature, such as in the computing industry. Cleanrooms are used most often during the creation of microchips and pharmaceuticals, but are used widely in a variety of other important industries. Cleanrooms are designed by mechanical engineers. The geographic location with the highest concentration of cleanrooms is California's Silicon Valley area.
Cleanrooms first came into use in the early 60s. In 1961, Willis Whitfield from Sandia Laboratories, in cooperation with colleagues, devised a novel ventilation concept - the idea of a "unidirectional" or "laminar flow" air supply - air pouring in one way and getting sucked out through an exhaust port on the opposite side of the room. Because the flow is laminar, like the center of a river, it allows the removal of a significant percentage of airborne particles which would otherwise be caught in the eddies and vortices of a conventional ventilation plan. This advance allowed the creation of rooms with very low levels of airborne contaminates relative to prior standards. In a laminar flow cleanroom, air is pumped into a room through a bank of HEPA (high efficiency particulate) filters. Because the air flow must be kept thoroughly unidirectional, only one wall or ceiling serves as the continuous source of clean air, with the opposite wall or floor serving as an exhaust grille to remove excess air and keep the flow moving.
The cleanliness of any unidirectional flow cleanroom is directly proportional to the velocity of the air moving through the room. Because the air volumes supplied to unidirectional flow rooms are many times (10-100) greater than those supplied to conventionally ventilated rooms, the capital and operating costs for the construction of such rooms can be very high. But many thousands of such rooms have been built since the 1960s, at various levels of cleanliness, and as an increasingly larger portion of our economy becomes dependent on the manufacture of delicate, contamination-sensitive products, the use of cleanrooms will only continue to increase.
