Pass box is a critical part of the product transfer which occur in every clean room. The use of pass box is essential to the maintenance of high level of cleanliness within the clean room. The pass box significantly limits the amount of outside air exposed in the clean zone during transfer of material.

With the use of either a mechanical or electrical interlock system, the clean room is protected from cross contamination which occur when both door were to open simultaneously or large parts and for wheeled carts.