Design of Laminar Flow Clean Benches
In a conventional laminar flow clean bench, particulates may contaminate the work area when hands or materials are placed inside the hood. The resulting turbulence creates backwash which allows dirty room air to enter the zone
Clean Bench Airflow
Particle-free air quality in the laminar flow clean bench is accomplished with precise control of airflow volumes and velocities. Any obstruction will have a significant impact on laminar flow performance. Obstructions include work in process or materials placed inside the hood or on the hood surface.
Obstructions cause interruptions in airflow which allow particulates to enter the work area or clean room, sharply increasing particle counts inside the hood. Backwash is the general term applied to the entry of unfiltered room air into the work area and may be created when the user inserts a hand or materials into the work area.
High velocity return air slots can minimize particulate contamination created by backwash common in conventional clean bench construction. Air is drawn into the high velocity slots located along the front edge of the work surface and along the side walls at 1,000 FPM ensuring that no unfiltered air enters the work area. These slots radically reduce particle counts from backwash created by the introduction of work pieces or operator’s hands into the work stream because they recover air at all leading edges of the work space, and recirculate the air through the HEPA filter to reduce the particle count. Slots help extend filter life by reducing the proliferation of dirty air into the filter intake.
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