ASHRAE Journal - November 2019 - 39

ASHRAE - CELEBRATING 125 YEARS

Contamination and Contamination Control
Contamination is an impurity, or some other undesirable
element, that soils, infects, makes unﬁt, or makes inferior
a material, a physical body, a natural environment, a
workplace, a product, etc. The contamination may be
viable, such as bacteria, microbes or viruses, or it may be
in the form of nonviable particles such as metals, organic
or inorganic compounds, pollution or dust. Airborne
contamination may also be gaseous or molecular contamination. Contamination may be brought into a space
by people, materials and equipment and/or airborne
contaminants located outside the space. Controlling contamination in a space is accomplished in two major ways:
prevention of contamination from entering the space
and prevention of contamination generated within the
space from contaminating a person, product or material.
People, equipment and materials can be cleaned prior
to their introduction into the space. Proper ﬁltration
and the use of positive pressure can mitigate airborne
contamination.

Hospitals
Hospitals were the ﬁrst spaces to attempt to control the
air where patients were located. Controlling the ventilation of hospital spaces was seen in ﬁrst-century Roman
military hospitals. Over the centuries, hospitals were
large, open halls that were well heated and ventilated.
Florence Nightingale made dramatic improvements in
the mortality rates of wounded soldiers by insisting on
scrupulously clean, well-ventilated hospital rooms.2
Louis Pasteur is remembered for his breakthrough in
the causes and prevention of diseases. His medical discoveries provided direct support for the germ theory of
disease and its application in clinical medicine. Pasteur
performed experiments that showed that without contamination, microorganisms could not develop. He
demonstrated that in sterilized and sealed ﬂasks, nothing ever developed, and in sterilized but open ﬂasks,
microorganisms could grow.3
The control of infection during surgery was a signiﬁcant driver to controlling contamination. Early pioneers
included British surgeon and advocate of antiseptic
surgery Joseph Lister, who pioneered the use of disinfectants; American surgeon William Keen and his efforts at
cleaning the surgical suite; and German Gustav Neuber,
who in 1883 designed a "cleanable" surgical suite containing nonporous surfaces, glass and metal furnishings

and in-room sterilization equipment. Neuber-style
surgery suites were adopted in many locations.4 These
early innovations provided guidance to manufacturers
also concerned with controlling contamination in their
precision manufacturing operations.

Precision Manufacturing and Contamination Control
Many manufacturers understood the need to keep particles out of the products they were building. Increased
cleaning was an obvious solution, but preventing the
particles from entering the space proved more challenging. Contamination in the manufacturing process
results in defects and unﬁt products. Precision manufacturing operations, such as watch making and ball
bearing manufacturing, were early adopters of contamination control techniques and the need to clean materials and have clean workstations.
In the latter part of the 1800s, Aaron Dennison and
Edward Howard relocated their watch factory from
downtown Roxbury/Boston, where trafﬁc on unpaved
roads was disastrous to the precise watch parts, to the
suburbs of Waltham to avoid the heavy dust. During
World War II the need for more precise military parts
increased the demand for clean manufacturing environments. Precision bearings were used in gyroscopes and
bomb sites before and during World War II.4
After the war the U.S. military continued to develop
advanced aircraft with advanced guidance systems
and miniature parts. 1947 saw the invention of the ﬁrst
transistor, and by the mid 1950s The New York Times spoke
about 'the business of making things smaller' as central
to new aircraft performance. Two years later Time magazine hailed miniaturization as a key to business growth;
acknowledging that military needs drove the trend, it
forecast that 'miniaturization will in time spread through
civilian U.S. life.' Already, pocket radios, tiny hearing aids
and other electronic devices had grown smaller; in the
future, so too would 'giant electronic brains.' 4

Early Cleanrooms
Similar to surgery suites, manufacturers needed a
special room where they could control contamination. Constant cleaning, while effective, was not very
productive. Manufacturers of precision military products started to request designs for "ultra-clean" rooms
and "white rooms" (or cleanrooms). Some claim that
Western Electric's "dust-free" room built in 1955 was the
N O V E M B E R 2 0 19

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ASHRAE Journal - November 2019

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