Unidirectional-Flow Clean-Air Devices maintain the highest level of control. Usually they are self contained units with a blower and an ULPA filter. The airflow is designed to sweep any micro-contamination away from the critical point. Since all the air is moving in the same direction, contamination does not recirculate to adjacent areas. This type of airflow design is used to achieve ISO 14644-1 class 5 and cleaner. Cabinets with this airflow design provide a local zone in a controlled area to protect the most critical operations.
The performance of Unidirectional-Flow Clean-Air Devices depends on the integrity of the ULPA filters, the velocity and uniformity of the airflow and the influence of the local environment in which it is placed. The various performance tests and acceptance criteria are set out in ISO 14644-3:2005, IEST-RP-CC002.3 and IEST-RP-CC034.3.