In the realm of cleanroom technology, FFU (Fan Filter Unit) and HEPA (High-Efficiency Particulate Air)  filter are vital components. While both serve to maintain air purity and control contamination, they differ significantly in structure, functionality, and application. FFUs are all-in-one air purification devices that provide uniform airflow distribution and maintain a consistent level of air cleanliness. HEPA filters, on the other hand, are standalone components designed for particle removal. 

I. Introduction to Structure and Function The Pass box is a special device used to transfer items between clean rooms and non-clean rooms, or different cleanliness levels within clean rooms, in order to reduce the number of times the clean room is opened and minimize contamination. Its structure usu