A fan filter unit (FFU) is a type of motorized

air filter A particulate air filter is a device composed of fibrous, or porous materials which removes particulates such as smoke, dust, pollen, mold, viruses and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbo ...

ing equipment. It is used to supply purified air to

cleanroom A cleanroom or clean room is an engineered space that maintains a very low concentration of airborne particulates. It is well-isolated, well-controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientifi ...

laboratories A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which science, scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as s ...

, medical facilities or microenvironments by removing harmful airborne particles from recirculating air. The units are installed within the system's ceiling or floor grid. Large

s require a proportionally large number of FFUs, which in some cases may range from several hundred to several thousand. Units often contain their own pre-filter, HEPA filter and internally controllable fan air distribution.

Design

FFUs are typically manufactured in 4' x 2', 3' x 2', or 2' x 2' steel housings, which can be placed in ceiling grid bays of similar dimensions. Units often contain a pre-filter as well as a HEPA (high-efficiency particulate air), ULPA (ultra-low particulate air) or other

MERV Merv (, ', ; ), also known as the Merve Oasis, was a major Iranian peoples, Iranian city in Central Asia, on the historical Silk Road, near today's Mary, Turkmenistan. Human settlements on the site of Merv existed from the 3rd millennium& ...

(minimum efficiency reporting value) filter. A motorized fan is used to pull air through the filters for distribution to rooms or enclosed work stations such as hoods. Fan speed is typically controlled via a step-wise or rheostat motor adjustment. Desired cleanliness levels determine the filter used: HEPA filters remove particles 0.3 μm or larger at 99.99% efficiency, while ULPA filters remove particles 0.12 μm or larger at 99.999% efficiency. FFUs are engineered for laminar air flow, as is required in critical environments. Controlled air flowing in a uniform direction and speed (carrying microparticles) is cleaner than turbulent air that flows in multiple directions or at inconsistent speeds. Eddies created by turbulent air cause contaminating microparticles to settle on clean surfaces.

Uses

4' x 2' or 2' x 2' FFUs are designed to be placed in ceiling grid bays with similar dimensions. Ceiling grids with standard size bays that match FFU dimensions are used to construct cleanrooms. Depending on the cleanliness requirements of the controlled space, more fan filter units can be added to the grid in order to meet ISO standards for airflow velocity and air changes per hour. FFUs can be used in place of a more conventional recirculating air unit such as a ducted or plenum air system. As FFUs require space above the ceiling grid (13" for the FFU module plus another 1–2 feet of "empty" air-filled space), plenums are commonly used for clean rooms with height restrictions; they are the only air systems that work in layouts with smaller internal floor dimensions. Additionally, when less than 20 filters are installed in a room, a fan- powered HEPA, FFU is generally considered to be less expensive than a more conventional ducted supply system. When a microenvironment of clean air is required, FFUs can be used to construct enclosed work spaces, or laminar flow cabinets. Applying the same principle as the larger cleanroom grid, FFUs can be placed directly in a free- standing grid above the space that requires clean air. In fact, this approach is also used for silicon wafer etching in the semiconductor industry.

References

External links

Negative Ion GeneratorAir Purifier Information
{{HVAC Air filters