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Cleanrooms;
Winter2006 issue
of Air Media
Author(s):
David Brande, Contamination Control Technologies, Inc.
Top of
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Cleanrooms, Minimum Testing Criteria
(Ed.
Note: The largest number of cleanrooms is divided between
the semi-conductor industry, driven by increased yield (or
decreased cull rates), and the pharmaceutical/ medical
device industry driven by health-related concerns of not
causing death or illness to the public along with FDA
regulatory concerns. In this article, Mr. Brande presents
his views on what the absolute minimum testing criteria
should be for a cleanroom to be “certified.”)
There are five tests
and/or calculations that must be performed in order to prove
four objectives that qualify a cleanroom as functional:
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One |
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Demonstrate
that the controlled area meets the desired
classification (Class ISO 5; Class ISO 6; Class ISO
7 or Class ISO 8). |
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Required Test |
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Room
classifications according to ISO 14644-1, or the now
defunct Federal Standard 209E, to establish that the
desired room class has been met. |
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Two |
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Demonstrate
that no particulate will enter the controlled area
by way of the supply air mechanical system. |
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Required Test |
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Integrity
testing of the HEPA filtered supply (or exhaust) air
with an oil aerosol (ambient challenge not accepted
here) to show no bypass of airflow and potentially
detrimental particulate. |
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Three |
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Demonstrate
that no particulate will enter (positive) or exit
(negative) the controlled area due to construction
(wall and/or ceiling utility penetrations, mouse
holes and threshold gaps). |
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Required Test |
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Differential pressures will indicate that both
direction and magnitude of static pressures is
sufficient to control migration of particulate from
one controlled area to another (or even an
uncontrolled area). |
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Four |
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Demonstrate
that, should there be an episode of particulate
generation within the controlled area, the design of
the room will handle the particulate in a
“controlled” and timely manner. |
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Required Test |
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Controlled
area volumes (sometimes recorded in the form of
velocities and converted) and subsequently the room
air exchange rates are used to determine if there is
sufficient airflow into a controlled area to
neutralize (dilute) any short term potential source
of particulate in an area and also maintain the
required static pressures. |
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Five |
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Required Test
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Finally,
air flow visualization (a picture is worth a
thousand words) for the definitive answer as to
whether a controlled area can truly control
particulate.
“If I could
perform only one test in a Class ISO 5 (Class 100)
environment, this would be my choice. In my opinion,
more pertinent information can be derived from this
test than all of the other standard tests listed in
either IEST-RP-CC006.3 or ISO 14644 Part 3.”
Note: In
areas Class ISO 6 (Class 1000) and higher, this
test takes on another form called room recovery
and is not quite so ‘visual’. Bear in mind, that
both tests are considered destructive in terms
of trying to maintain sterility.
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