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Dynamic Pass Box

A dynamic pass box refers to a pass box in which the internal airflow is dynamic, featuring a self-circulating airflow pattern. Clean air is supplied into the chamber while contaminated air is expelled, maintaining cleanliness inside the pass box.

The dynamic pass box is equipped with a fan and a filter. The fan draws air in, and the filter purifies the air before blowing it into the pass box, pushing contaminated air out through the exhaust port, thus creating a continuous circulation.

Compared to a static pass box, the dynamic pass box includes an additional air filtration process and components that provide self-circulating airflow. Therefore, for the same internal dimensions, the external dimensions of a dynamic pass box are larger, and its manufacturing cost is higher than that of a static pass box.

Classification of Dynamic Pass Boxes

Dynamic pass boxes can be further divided into laminar flow pass boxes and air shower pass boxes.

Laminar Flow Pass Box

A laminar flow pass box provides vertical laminar airflow. From top to bottom, the pass box is sequentially equipped with a fan, a filter, and a flow straightener (perforated plate/flow homogenizing film). The internal airflow follows a top-supply, bottom-return pattern. The airflow velocity from the flow straightener meets laminar flow requirements.

Air Shower Pass Box

Unlike the laminar flow type, the air shower pass box is not equipped with a flow straightener. Instead, it features circular nozzles at the air outlet. During operation, clean air filtered by the HEPA filter is blown out from the nozzles at a velocity of no less than 25 m/s (typical value), dislodging dust particles from the surface of the items being transferred. The dislodged contaminants are then expelled through the air outlet or recirculated to the air intake, filtered again, and blown out through the nozzles. This cycle forms a micro self-circulating clean environment.