Basic Documentation

Clean Rooms
• Construction Procedures—Clean rooms must be constructed using specialized
techniques and practices to prevent contamination of the room materials, ventilation
ductwork, and room equipment. Room components, such as ductwork, must be pre-
cleaned and sealed before installation so that no residual particulate is present.
Construction personnel must be properly trained and must follow rigid guidelines for
handling construction materials and equipment, and in carrying out construction
procedures. Typically, they must wear outer garments that protect against bringing
contaminants into the clean room during the construction process. Tools and
construction equipment must meet a specific level of cleanliness before they may be
brought into the clean area.
• Room Utilization Procedures—Clean room access must be restricted to authorized
personnel only. Such persons must be properly trained in acceptable procedures and
work practices. Specialty outer garments are usually required. Occupants must not
consume food in the clean room. Special room cleaning, maintenance, and
decontamination processes must be used. Room entry decontamination procedures
must be followed.
• Ventilation & Directional Airflow—Clean rooms typically require very high rates of
HEPA or ULPA
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filtered ventilation airflow to maintain the required low level of
airborne particulate in the room atmosphere. Airflow is typically from ceiling to floor in
a laminar airflow arrangement that most often uses the entire ceiling as a supply
plenum and filter bank.
• Room Pressurization—Proper differential pressurization has been found to be very
effective and an absolutely necessity for preventing contamination in clean rooms. All
clean rooms and surrounding areas must be maintained at specific levels of
pressurization to ensure against improper directional airflow. Two, three or more
levels of positive pressurization may be used in clean room applications with the
most critical area at the highest positive pressure level and the adjacent areas or
support at lower positive pressure levels. Adequate levels of differential
pressurization and proper directional airflow are especially critical at the room entry
and exit points.
Clean Room Standards
Clean room purity is classified in accordance with the maximum allowable concentration of
airborne particulate per cubic foot or cubic meter. Two standards set clean room
classifications: FS 209E and ISO/FDIS 14644-1. FS 209E is a United States Federal
Standard that was initially issued in the 1960's and was last revised in 1992. Up until 1999 it
was the only recognized clean room standard. It is still widely used today, especially where
U.S. Governmental regulations and interests are involved. However, in 1999 the international
standard, ISO/FDIS 14644-1 was adopted and is likely to eventually replace the FS 209E
standard.
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HEPA - High Efficiency Particulate Air filters remove at least 99.97% of particulate 0.3 microns (0.3µm) or larger in size.
ULPA - Ultra Low Penetration Air filters remove 99.999% of particulate 0.12 microns (0.12µm) or larger on size. A micron (µm)
is one millionth of a meter or approximately 0.00003937 inches.
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