Airflow Pattern Test
An airflow visualization (smoke pattern test) should be used to train and instruct compounding personnel in proper aseptic technique for every primary engineering controls (PEC) in which they work. Working in a horizontal flow Laminar Air Flow Workstation (LAFW) is different that working in a vertical flow Biological Safety Cabinet (BSC) or Compounding Aseptic Isolator (CAI). Airflow must be traced from the entrance plane (HEPA filter diffuser) across the Direct Compounding Area (DCA) to the exit plane. The DCA is the area within the PEC where critical operations are conducted.
- The entrance plane in a horizontal flow LAFW is the HEPA filter at the rear of the work surface. The exit plane is the area behind the operator. Air must be traced from the HEPA filter diffuser screen across the critical sites in the DCA to and across the operator and should not reflux back into the work area after passing through it.
- The entrance plane in a vertical flow unidirectional airflow device is the HEPA filter diffuser screen above the work surface. In a unidirectional vertical flow area, the diffuser screen will traverse the entire entrance plane from the front wall to the back wall and from side wall to sidewall. The exit plane in a vertical flow device is the work surface. Air must be traced from the diffuser screen across the critical sites in the DCA to and into the air grilles at the front and rear of the work surface.
- The air in the center of the work area at the work surface of a vertical flow device is typically the worst airflow in many devices.
- The air closest to the front intake grille is often the best airflow within a vertical flow device.
- In both vertical and horizontal airflow, the airflow through the DCA must be shown to be smooth and without turbulence and updrafts.
- Air must be shown to sweep across the critical site.
- Air flowing out of the HEPA filter diffuser screen is considered “First Air” until hits an obstruction such as an IV bar, the operator’s hands, vials, bags, and other supplies. “First Air” must be proven to exist at all critical sites.