Filter Fan Units (FFU) with integrated high-performance HEPA filters are installed in the cleanroom ceiling, which draw in the air, filter it and blow it into the cleanroom at the desired pressure. The low-particle air flow, also known as laminar flow, displaces the particle-laden air in the cleanroom and directs it back into the recirculating air walls through outflow openings in the floor.
However, simpler systems such as cleanroom tents or CNC Cleanrooms can also be operated without an air recirculation system. In these cases, 100% of the clean air is discharged via discharge grilles, process openings or the floor gap.