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HEPA filtration and the development of cleanrooms: A brief history

Author: Candice Goddard

According to Tim Sandle’s 2016 article: ‘The development of cleanrooms: a historical review. Part 1: From civil war to safe surgical practice;’ it is difficult to pinpoint the exact date the cleanroom was developed. We can, however, go back in history and look at when advances in clean air technology took place. Sandle goes on to explain that these developments were mostly driven by two different fields that sought to control environmental contamination within their working spaces.

In the field of medicine, it had been shown that environmental contamination was compromising the success of medical procedures, as well as the success of patient recovery post procedure. For this reason, persistent effort and research went into creating a sterile environment for operations performed on patients.

In the military sector, dust particulate posed a threat to the functioning of intricate components used in the engineering of weapons.

The second World War (WWII) saw great technological development in weaponry. These developments called for cleaner production and assembly areas. As described in an excerpt from Sandle’s article: ‘the need to assemble small-sized critical components, from gun mechanisms to aircraft gyroscopes, in areas free from contamination led to the development of “white rooms”.’ (Sandle,2016, para 13)

These “white rooms” were mechanically ventilated by units equipped with what was then known as “absolute filters.” The filters were developed as part of the classified weapons Manhattan Project, but the filter technology was later declassified and made available for widespread use. The Acronym HEPA replaced “absolute filter” during this time in the 1950’s, and these highly efficient filters became a crucial part of clean air technology.

During this time, various industries started building and using turbulent cleanrooms for their manufacturing processes. As described with “white rooms,” turbulent cleanrooms introduced air from the atmosphere into the cleanroom area, after the air had gone through HEPA filtration.

Further experimentation led to the introduction of low-level extraction systems that were used in conjunction with the introduced HEPA filtered air; this was done to direct the flow of filtered air, and to better control dust particulate.

Fast forward to the 1960’s, and we see major innovation. Willis Whitfield, while working at Sandia National Laboratories, headed a team that used HEPA filters to create unidirectional airflow. As Sandle explains in his works: ‘the concept of laminar airflow is that air is introduced into the cleanroom at a high velocity which causes the air to travel along a unidirectional path over a required distance.’ (Sandle,2016, para 20)

The process described above ensures that no contaminants enter the working area covered by the laminar airflow; a process that went on to revolutionize sterility in hospital operating theatres.

In 1961, Professor Sir John Charnley, an orthopaedic surgeon living in the UK, along with his colleague, Hugh Howorth, applied the technology of downward flowing HEPA filtered air to cover the operating table in a theatre. Because the HEPA filtered unidirectional airflow was positive to that of the surrounding ambient air, contaminants were kept out; including those generated by the surgeons during procedure. They saw an increase in patient recovery post procedure, and improvement in infection rates during operations. This led to a widespread following from other hospitals, who then incorporated laminar airflow over their operating tables.

To summarize, cleanroom technology developed quickly once the wheels of research and application were in motion. While the fields of medicine and military were the driving forces; aeronautics, motor vehicle manufacturing, pharmaceutical production lines, and nuclear science were some of the other industries that adopted and benefitted from HEPA filtered cleanrooms.

These benefits continue into today as we live in an age of high-tech engineering, advanced electronics, and incredible medical progresses that have increased our life expectancy with each passing decade.

In our next article, we look at how the cleanliness in these cleanrooms went on to be standardized, and the classification of cleanrooms followed.

Stay tuned…

References & Credits:

Sandle, T. (2016). The development of cleanrooms: a historical review. Part 1: From civil war to safe surgical practice.


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