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History of Cleanrooms CELEBRATING125 YEARS This article was published in ASHRAE Journal, November 2019. Copyright 2019 ASHRAE. Posted at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE. For more information about ASHRAE Journal, visit www.ashrae.org. History of Cleanrooms BY PHILIP NAUGHTON, MEMBER ASHRAE Cleanrooms are areas in which particle concentration and environmental conditions are controlled within specified limits. The limits of the particle concentrations are normally set by the requirements of the process occurring within the space so that contamination of people, processes and equipment can be mitigated. Today clean- room applications have increased from its early days in hospitals and precision manu- facturing to include:1 • Pharmaceuticals/Biotechnology. Preparations electronic and nanotech applications, medical device of pharmaceutical, biological and medical products manufacturing, automotive paint booths, crystal, laser/ require clean spaces to control viable (living) and non- optic industries, and advanced materials research. viable particles that could impact product sterility. Design of clean spaces covers much more than tradi- • Microelectronics/Semiconductors. Feature sizes in tional control of particles concentrations. Controlling semiconductors are smaller than many molecules, and other environmental parameters may also be necessary controlling the concentration of particles pushes these to a process within the clean space. Additional factors cleanrooms to limits of cleanroom technology. may include air temperature and humidity; electrostatic • Flat Panel Display: flat panel display (FPD) facto- discharge (ESD); molecular and gaseous contamination; ries are some of the largest cleanrooms in the world, airflow patterns; air pressurization; sound and vibration. with some cleanroom spaces greater than 2,000,000 ft2 The objective of good cleanroom design is to maintain (200,000 m2). New FPD factories are controlling par- effective contamination control while ensuring required ticles and chemical concentrations. levels of reliability, productivity, installation and oper- • Aerospace. Cleanrooms were first developed for ating costs. Cleanrooms are a specially constructed aerospace applications to manufacture and assemble enclosed space with environmental control of particu- gyroscopes, precision ball bearings, satellites and aero- lates, temperatures, humidity, air pressure, airflow space electronics. patterns, air motion, vibration, noise, viable organisms • Hospitals. Controlling infection during surgery was and lighting (ASHRAE, 2018).1 Cleanrooms are used in the driver for many early contamination control tech- advanced manufacturing, controlling contamination to niques. the manufacturing process and in medical operations • Miscellaneous Applications. Cleanrooms are also where controlling the spread of infection is of utmost used in aseptic food processing and packaging, micro- importance. Philip Naughton is a senior engineer and energy manager for Applied Materials Inc. He is past chair of ASHRAE TC 9.11 Clean Spaces, and is current subcommittee chair for TC 9.11 Energy Efficiency for Cleanrooms and is ASHRAE liaison to U.S. TAG for ISO 14644 Cleanrooms and Associated Controlled Environments. He also participates in other committees and industry activities related to cleanrooms. 38 ASHRAE JOURNAL ashrae.org NOVEMBER 2019 ASHRAE — CELEBRATING 125 YEARS Contamination and Contamination Control and in-room sterilization equipment. Neuber-style Contamination is an impurity, or some other undesirable surgery suites were adopted in many locations.4 These element, that soils, infects, makes unfit, or makes inferior early innovations provided guidance to manufacturers a material, a physical body, a natural environment, a also concerned with controlling contamination in their workplace, a product, etc. The contamination may be precision manufacturing operations. viable, such as bacteria, microbes or viruses, or it may be in the form of nonviable particles such as metals, organic Precision Manufacturing and Contamination Control or inorganic compounds, pollution or dust. Airborne Many manufacturers understood the need to keep par- contamination may also be gaseous or molecular con- ticles out of the products they were building. Increased tamination. Contamination may be brought into a space cleaning was an obvious solution, but preventing the by people, materials and equipment and/or airborne particles from entering the space proved more chal- contaminants located outside the space. Controlling con- lenging. Contamination in the manufacturing process tamination in a space is accomplished in two major ways: results in defects and unfit products. Precision manu- prevention of contamination from entering the space facturing operations, such as watch making and ball and prevention of contamination generated within the bearing manufacturing, were early adopters of contami- space from contaminating a person, product or material. nation control techniques and the need to clean materi- People, equipment and materials can be cleaned prior als and have clean workstations. to their introduction into the space. Proper filtration In the latter part of the 1800s, Aaron Dennison and and the use of positive pressure can mitigate airborne Edward Howard relocated their watch factory from contamination. downtown Roxbury/Boston, where traffic on unpaved roads was disastrous to the precise watch parts, to the Hospitals suburbs of Waltham to avoid the heavy dust. During Hospitals were the first spaces to attempt to control the World War II the need for more precise military parts air where patients were located. Controlling the ventila- increased the demand for clean manufacturing environ- tion of hospital spaces was seen in first-century Roman ments. Precision bearings were used in gyroscopes and military hospitals. Over the centuries, hospitals were bomb sites before and during World War II.4 large, open halls that were well heated and ventilated. After the war the U.S. military continued to develop Florence Nightingale made dramatic improvements in advanced aircraft with advanced guidance systems the mortality rates of wounded soldiers by insisting on and miniature parts. 1947 saw the invention of the first scrupulously clean, well-ventilated hospital rooms.2 transistor, and by the mid 1950s The New York Times spoke Louis Pasteur is remembered for his breakthrough in about ‘the business of making things smaller’ as central the causes and prevention of diseases. His medical dis- to new aircraft performance. Two years later Time maga- coveries provided direct support for the germ theory of zine hailed miniaturization as a key to business growth; disease and its application in clinical medicine. Pasteur acknowledging that military needs drove the trend, it performed experiments that showed that without con- forecast that ‘miniaturization will in time spread through tamination, microorganisms could not develop. He civilian U.S. life.’ Already, pocket radios, tiny hearing aids demonstrated that in sterilized and sealed flasks, noth- and other electronic devices had grown smaller; in the ing ever developed, and in sterilized but open flasks, future, so too would ‘giant electronic brains.’ 4 microorganisms could grow.3 The control of infection during surgery was a signifi- Early Cleanrooms cant driver to controlling contamination. Early pioneers Similar to surgery suites, manufacturers needed a included British surgeon and advocate of antiseptic special room where they could control contamina- surgery Joseph Lister, who pioneered the use of disinfec- tion. Constant cleaning, while effective, was not very tants; American surgeon William Keen and his efforts at productive. Manufacturers of precision military prod- cleaning the surgical suite; and German Gustav Neuber, ucts started to request designs for “ultra-clean” rooms who in 1883 designed a “cleanable” surgical suite con- and “white rooms” (or cleanrooms). Some claim that taining nonporous surfaces, glass and metal furnishings Western Electric’s “dust-free” room built in 1955 was the NOVEMBER 2019 ashrae.org ASHRAE JOURNAL 39 ASHRAE — CELEBRATING 125 YEARS 5 first production cleanroom. The mechanical ventilation. Another Figure 1 1936 Operating room showing UV lamps. Western Electric room was designed important step in the field of air- Air inlet in the upper left.7 using 99.95% filters (see sidebar, borne infections was the use of History of HEPA Filters, Page 42) and ultraviolet lighting in combination positive pressurization. Others have with mechanical ventilation. Deryl claimed the Olmsted Air Force Base Hart found that ultraviolet light in Pennsylvania or the U.S. Navy’s would reduce the airborne bacteria North Island Naval Air Station in in the operating room.7 While the San Diego were the home of the first use of UV lighting was not directly installations.6 part of the ventilation system, it was integrated with the ventilation Convergence of Ideas system to ensure adequate mixing While advances in contamination of the air. An operating room at the sufficient volume to produce 480 control were occurring in manufac- Hospital for Sick Children in Toronto air changes per hour. The results turing operations during the 20th combining air-conditioning ultra- indicated significant reduction in century, the medical profession was violet lamps was constructed in 1936 airborne contamination.7 also experimenting with new con-
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