The clean rooms: history and modernity
Maria Kiryushina, specialist of SEZ "Technopolis "Moscow" press service.
Clean room is a special room, where air supports predetermined size and number of the particles per cubic meter - dust, bacteria, aerosol and vapors of chemical elements. Usually, humidity, pressure and temperature are controlled. The structure of the clean room is specific and this minimizes the introduction and generation of particles within it. Clean rooms are necessary for microelectronics, optics, biotechnology, production of medical products and medicines, research experiments, food industry. Each of these areas has its own requirements of purity class.
In the 1860s, Joseph Lister, an English surgeon and scientist, the Creator of surgical antiseptics, put forward the "theory of purity". It is stated that the removal of bacteria from operating rooms and hospitals should prevent infections and postoperative complications. For disinfection, carbolic acid was sprayed and a unidirectional air flow was arranged. During the Second world war, the need for decontamination during medical procedures has become particularly acute. As a result, the system of forced ventilation was developed.
In the 1940s, air HEPA filters were invented, which were originally used to trap radioactive particles, and then began to be used in hospital ventilation systems. At the same time in the United States in the factories of General Electric, which produced ball bearings for gyroscopes, there are new production facilities. Their necessity was dictated by a large number of defects - dust particles became the cause of defects. The air flows on the work sites were distributed in different directions, and the walls were made of stainless steel. The company's specialists in protective suits controlled the technological process outside the clean zone.
A new impetus in the development of clean rooms is associated with the name of the Sandia Laboratories employee - Willis Whitfield. He concluded that the dust not only comes from the outside, but also occurs inside. Microscopic particles of clothing, human skin, equipment can be in the room for a long time. Whitfield began to supply clean air into the room in one horizontal direction through several HEPA filters and output an equal amount of air out. He also directed a vertical laminar air flow from top to bottom - with the force of gravity neutralizing the flying particles. The concept of clean room ventilation with unidirectional air flow was quickly supported by many industries - pharmaceuticals, microelectronics - wherever there was a need for high-purity premises. The ideas proposed by Whitfield, remained unchanged to date, transformed only the processes and mechanisms of their implementation through the development of technology.
Clean room design
Clean room has a special structure that meets the needs of different industries. The rules of cleanliness are established according to official standards.
Clean rooms include a work area and air conditioning and cleaning systems. Walls and floor, ceiling systems, internal partitions are made of smooth materials that do not accumulate and do not emit dust particles. The components of the structure have high strength, moisture resistance, anti-static properties, meet safety requirements. Employees are dressed in special clothing that is not able to generate dust fragments. The main task of the room elements is to make it a sealed, closed, clean space.
These requirements are relevant for all types of clean rooms, including those built as a "room in a room" - in this case, the working and technical area are located on the same space. At the same time, the working area with an Autonomous ventilation and lighting system and a higher class of cleanliness is in the center and on four sides is limited to sealed wall panels.
In order to create exemplary conditions of cleanliness for a particular technological process, the requirements for materials, structure, equipment of a clean room are determined individually, based on the requests of production.
Classification of clean rooms
Nowadays, there are two clean room classification systems in use - the pan-European CEN and the international ISO. In Russia, as a rule ISO 14644-1 typing is used, in which there are nine classes of cleanliness from ISO 1 to ISO 9. The number here determines the maximum allowable concentration of aerosol particles of a given size per cubic meter. The higher the sterility class, the smaller the quantity of undesirable elements in the air. There are also classes of purity according to GMP requirements (from the English. good manufacturing practice-good manufacturing practice) - they put forward conditions for the exclusion of foreign particles in the manufactured products. As already noted, in a clean room in a low class can be a clean zone of a higher class. For example: on the site of SEZ "Technopolis "Moscow" in printers work clean rooms for companies engaged in microelectronics and biotechnology. For the production of microelectronics is supported by the purity class ISO 7 with the possibility of increasing one of the blocks up to class ISO 5, and for activities in the field of biotechnology acting the cleanliness class C according to GMP standards (domestic and foreign certificates of conformity).