Clean Air Products CAP301
Series horizontal laminar
flow clean bench.
Aclean bench (also called a laminar flow bench or laminar flow workstation) is a piece of equipment designed to create a micro-envi- ronment that meets industry standards for
particulate control. Clean benches range in size from
compact tabletop versions to larger cabinets. Many
manufacturing environments, such as semiconductor, pharmaceutical, medical device, food, aerospace, and nanotechnology production, require that
products be kept free of particulate contamination.
Laboratories and test and inspection areas are also
common sites for clean benches. Clean benches are
a convenient method of creating a Class 100 (ISO 5)
or Class 10 (ISO 4) clean air environment within a
larger work area.
Clean benches can be used as stand-alone solutions or they can be installed inside a cleanroom. It
is often more economical to supplement a cleanroom
with clean benches to create localized Class 100 or
Class 10 areas, rather than make the entire cleanroom Class 100 or Class 10. When used outside a
cleanroom, a clean bench does not require a worker
to be gowned, although individuals often wear gloves
and arm coverings when using a bench as an extra
measure of protection against particulate contamination.
Key principals of clean bench performance
Clean benches employ two key principals that are
critical to maintaining a contaminant-free environment — laminar airflow and filtration.
Laminar flow refers to a state in which non-turbu-lent streams of air flow in one direction parallel to
one another. Laminar airflow is the most efficient
option for removing particulate contamination from
a controlled area because the airflow uniformity and
lack of turbulence keep clean air streams from mixing with and being contaminated by contaminated
air streams. An object being bathed with clean, turbulence-free, laminar airflow will remain clean and
protected from nearby contamination.
Clean benches with either vertical or horizontal laminar airflow provide the cleanest working
environments because HEPA-filtered air within
these benches is unidirectional and turbulence-free.
(Unidirectional is airflow having generally parallel
stream lines, operating in a single direction with uniform velocity over its cross section.)
The air that bathes a product in a clean bench needs
to be free of contaminants. This requires filtration.
Clean benches are usually classified according to the
number and size of particles permitted per volume
of air in a specific amount of time.
A HEPA (High Efficiency Particulate Air) filter is
often used to filter the air streams of a clean bench.
To qualify as HEPA by U.S. government standards,
an air filter must remove 99.97 percent of 0.3
micrometer particles. With the proper airflow and
HEPA-filtered air, a clean bench can be rated Class
100 or ISO 5 (99.99 percent are typically used).
An ULPA (Ultra-Low Particulate Air) filter can be
used when a Class 10 or ISO 4 rating is required. An
ULPA filter removes at least 99.999 percent of any airborne particles 120 nanometers (0.12 micron) or larger.
Considerations for specifying clean benches
There are many possible configurations for clean
benches. Specifying the ideal environment for a
particular application will require careful decisions
regarding airflow, bench design and filtration options.
Direction of laminar flow
The first decision a specifier of clean benches faces
is horizontal or vertical laminar flow. Vertical and
Clean Air Products
Selecting the right horizontal- or vertical-flow bench for your application.