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Introduction to History of Cleanrooms - Pharmaceutical HVAC
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Introduction to History of Cleanrooms



Like many other human inventions, the cleanrooms were originated during war conflicts. Some of them as inoffensive and useful like the zipper, passing through the radar, and others with as lethal consequences as the atomic bomb. Of course, there had been a concern about contamination in-room patients, but the military industry was the motor for developing the cleanroom technology during WWII and the cold war.

In this post, we will talk about the history of modern cleanrooms and will provide some literature for further references.

The beginnings


The development of the first cleanrooms for industrial manufacturing started during the Second World War, and developed during the Cold War, mainly to improve the quality and reliability of instrumentation used in aircraft, tanks, and other weapons. It was noticed, for instance, that bombsights were defective when dirtiness was introducing on their gyroscopes during manufacturing.

1945 Bombsight

Bombsight 1945

The key success for the development of the cleanrooms was the invention of the HEPA filters. But its origins deserves another post.

Probably the Western Electric production room was the first cleanroom at the height of the Cold War in 1955. It was designed with 99.95% HEPA filter and pressurization. The company was having a major problem in manufacturing missile gyroscopes. About 99% of gyroscopes were being rejected, the problem being identified as dust. It was decided that a ‘dust-free’ production room should be built, and this was designed by the AC Corporation.

Gyroscope production at Western Electric

Western Electric

The Willis Whitfield invention


The name of Willis Whitfield is associated with the inventor of the first unidirectional flow in 1961.

It was patented later in 1964, you can access the original document here:


The room was small, about 1.8 m × 3 m × 2.1 m. Instead of the air being supplied by ceiling diffusers and mixing with the room air in an uncontrolled manner, it was supplied by a bank of HEPA filters. This ensured that air moved in a unidirectional way from the filters, across the room, and out through the floor grilles.

The air velocity was about the famous 0.45 m/s (90 fpm), established since then as a standard in the old FED-STD-209A and still today being used. It was an empirical valued obtained considering turbulence, human comfort, and particle removal.

A later great contribution was the CG mesh, explained here

Whitfield cleanroom

Whitfield cleanroom

To know more


Cleanroom technology. Fundamentals of Design, Testing and Operation. William Whyte. Wiley.

History of Cleanrooms. Philip Naughton. ASHRAE Journal. November 2019

Controlling contamination: The origins of clean room technology. Daniel Holbrook. History and Technology. September 2009.

“Willis Whitfield, inventor of modern-day laminar-flow clean room, passes away”. Sandia LabNews. Volume 64, Number 22, November 2012

  • Jose Luis Ullibarri
    Posted at 10:01h, 02 September Reply

    La sala era tan pequeña que dio origen a la famosa sala Misterium.

    • Manel Fernandez
      Posted at 10:23h, 02 September Reply

      Efectivamente. No hay nada nuevo bajo el sol 🙂

  • DAvid Manzanares
    Posted at 09:14h, 04 September Reply

    M’encanta Manel, molt bon post.

  • Manel Fernandez
    Posted at 10:13h, 04 September Reply

    Gracies David

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