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Evolution of the Clean Room

Although the principles of clean room design go back more than 150 years to the beginning of bacterial control in hospitals, the clean room itself is a relatively modern development.

by John Buie

Although the principles of clean room design go back more than 150 years to the beginning of bacterial control in hospitals, the clean room itself is a relatively modern development. It was the need for a clean environment for industrial manufacturing during the 1950s that led to the modern clean room as we know it.

A clean room is a rigorously controlled environment that has a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapors. The air entering a clean room is filtered and then continuously circulated through high efficiency particulate air (HEPA) and/or ultra-low particulate air (ULPA) filters to remove internally generated contaminants. Staff wearing protective clothing must enter and exit through airlocks, while equipment and furniture inside the clean room is specially designed to produce minimal particles.

While more than 30 different industry segments utilize clean rooms, 70 percent of U.S. clean room floor space is in the semiconductor and other electronic components, pharmaceutical, and biotechnology industries.

1939 – 1945

Development of the modern clean room began during the Second World War to improve the quality and reliability of instrumentation used in manufacturing guns, tanks and aircraft. During this time, HEPA filters were also developed to contain the dangerous radioactive, microbial or chemical contaminants that resulted from experiments into nuclear fission, as well as research into chemical and biological warfare.

While clean rooms for manufacturing and military purposes were being developed, the importance of ventilation for contamination control in hospitals was being realized. The use of ventilation in a medical setting gradually became standard practice during this time.

1950s – 1960s

The evolution of clean rooms gained momentum as a result of NASA’s space travel program in the 1950s and 1960s. It was during this time that the concept of ‘laminar flow’ was introduced, which marked a turning point in clean room technology.

In the late 1950s, Sandia Corporation (which later became Sandia National Laboratories) began investigating the excessive contamination levels found in clean rooms. Researchers found that clean rooms were being operated at the upper practical limits of cleanliness levels and identified a need to develop alternative clean room designs.

In 1960, Blowers and Crew in Middlesborough, UK was the first to improve contamination control by creating a unidirectional airflow from an air diffuser fitted over the entire ceiling in an operating room. In practice, the airflow was disturbed by air currents and the movement of people, but the idea of unidirectional flow was born.

Also in 1960, McCrone Associates began developing advanced particle handling techniques using tungsten needles and collodion. These techniques, which later became industry standards, were incorporated into the McCrone Associates Class 100 clean room.

In 1961, Professor Sir John Charnley and Hugh Howorth, working in a hospital in Manchester, UK, managed to significantly improve unidirectional airflow by creating a downward flow of air from a much smaller area of the ceiling, directly over the operating table.

Also in 1961, the first standard written for clean rooms, known as Technical Manual TO 00-25-203, was published by the United States Air Force. This standard considered clean room design and airborne particle standards, as well as procedures for entry, clothing and cleaning.

In 1962, Sandia Corp. launched the Whitfield Ultra-clean room, which was publicized in Time Magazine, creating a great deal of interest. Instead of simply using filters to clean incoming air, Whitfield used filtered air to keep the room clean by introducing a change of ultra-clean air every six seconds.

In 1962, Patent No. 3158457 for the laminar flow room was issued. It was known as an “ultra clean room.”

By 1965, several vertical down flow rooms were in operation in which the air flow ranged between 15 m (50 ft)/min and 30 m (100 ft)/min. It was during this time that the specification of 0.46 m/s air velocity and the requirement for 20 air changes an hour became the accepted standard.

In 1966, Patent No. 3273323 was submitted and issued for the “laminar flow airhood apparatus.”


By the early 1970s the principle of “laminar flow” had been translated from the laboratory to wide application in production and manufacturing processes.

1980s – 1990s

The 1980s saw continued interest in the development of the clean room. By this stage, clean room technology had also become of particular interest to food manufacturers.

During the late 1980s, STERIS (formerly known as Amsco) developed the use of hydrogen peroxide gas for the decontamination of clean rooms, and marketed the idea under the trademark VHP (vaporized hydrogen peroxide). Hydrogen peroxide gas rapidly became the most widely used method of sterilization, due to its unique combination of rapid antimicrobial efficacy, material compatibility and safety.

In 1980, Daldrop + Dr.Ing.Huber developed an innovative clean room ceiling, known as ‘Euro Clean’, to meet the rising challenges from industry at the beginning of the 80s.

In 1987, a patent was filed for a system of partitioning the clean room to allow zones of particularly high-level cleanliness. This improved the efficiency of individual clean rooms by allowing areas to adopt different degrees of cleanliness according to the location and need.

In 1991, a patent was filed for a helmet system that can be used in a medical clean room in which the user is protected from contaminated air in the environment, while the patient is protected from contaminated air being exhausted from the user’s helmet. Such a device decreases the possibility of operating room personnel being contaminated with viruses carried by the patients being operated upon.

In 1998/1999, CRC Clean Room Consulting GmbH introduced the clean room filter fan. This involved the integration of a filter fan unit, with filter, ventilator, and motor directly into the clean room ceiling.


The pace of clean room technology transformation has accelerated over recent years. Since the year 2000, there have been significant advances in new clean room technology, which have helped to streamline manufacturing and research processes, while also reducing the risk of contamination. Most of the technological developments of the past decade have been directed towards the manufacture of sterile products, particularly aseptically filled products.

In 2003, Eli Lilly pioneered the development of a new system for the prevention and containment of crosscontamination during the manufacture of pharmaceutical powders using a specially designed ”fog cart”. This allows the operator to be covered by an exceptionally fine fog of water on exit from a critical area, virtually eliminating the risk of transferring dust traces beyond their proper confines.

In 2009, The University of Southampton, UK opened a Nanofabrication Centre containing a clean room with nanofabrication facilities, making it possible to manufacture high-speed and non-volatile ”universal memory” devices for industry that could process information faster than anything achieved with conventional technologies.

The Future of Clean Rooms

Clean room facilities in the United States have been predicted to grow fourfold from a baseline of 1998 to the year 2015, to an estimated 180 million square feet in 2015.

The most common applications of clean rooms currently are in the manufacture of semiconductor and other electronic components, as well as in the pharmaceutical and biotechnology industries. In addition to these traditional applications, clean room technology has more recently been applied to micro- and nano-system processes, and this looks certain to be an area of growth in coming years. The development of clean room technology is likely to continue to be driven by certain key factors including the increasingly technical use of exotic physical and biological phenomena, the central role of increasingly fine structures, the creation and use of materials of the highest purity, and the increasingly broad-based utilization of biotechnology. Given the scale of these challenges, clean room technology looks set to remain indispensable to production in coming years.

Photos courtesy of Terra Universal