Equipment laminar flow units

Filtered air may be used to purge a complete room, or it m be confined to a specific area and incorporate the principle of laminar flow, which permits operations to be carried out in a gentle current of sterile air. The direction of the airflow may be horizontal or vertical, depending upon the type of equipment being nsed, the type of operation and the material being handled. It is important that there is no obstruction between the air supply and the exposed product, since this may resnlt in the deflection of microorganisms or particulate matter fiom a non-sterile surface and canse contamination. Airflow gauges are essential to monitor that the correct flow rate is obtained in laminar flow units and in complete suites to ensure that a positive pressure fiom clean to less clean areas is always maintained. 

To support the institutional pharmacist in preparing IV admixtures (which typically involves adding one or more drugs to large-volume parenteral fluids), equipment manufacturers have designed laminar flow units, electromechanical compounding units, transfer devices, and filters specifically adaptable to a variety of hospital programs. 

A laminar flow enclosure provides a means for environmental control of a confined area for aseptic use. Laminar flow units utilize HEPA filters, with the uniform movement of air along parallel lines. The air movement may be in a horizontal or vertical direction and may involve a confined area, such as a workbench, or an entire room. Laminar flow modules are suspended above filling lines, vial- and stopper-washing equipment, and other processes to provide an aseptic and particulate-free environment. 

A complete visual representation of the manufacturing process in flow chart format should be included. This flow chart should indicate the step in the process, the equipment and materials used, and the room where the operation is performed, and should provide a complete list of the in-process controls and tests performed on the product at each step. The diagram should also include information, including a descriptive narrative, on the methods used to transfer the product between steps (i.e., sterile, SIP connection, sanitary connection, open transfers under laminar flow units, etc.). 

Workbenches, including laminar flow units, and equipment, should be disinfected immediately before and after each work session. Equipment must be of the simplest design possible for the operation being performed. 

The precise location of portable units must be defined. Laminar flow units, although creating a protected environment within their confines, may themselves create turbulence and dead air in the room in which they are situated and into which they exhaust. This may create a secondary source of contamination. The airflow patterns around laminar flow units relative to fixed air exit registers, screening, and other equipment in a room cannot be predicted. Empirical evidence from smoke pattern studies is necessary to be confident of their effectiveness. 

The testing of air permeability of nonwoven fabrics is defined in ASTM, ISO, ° and NWSP standards. The equipment includes the Frazier air permeability tester, the liquid expulsion porometer, and the water permeability tester for geotextiles. In the air permeability tests, the volumetric rate of airflow through a nonwoven fabric of unit cross-sectional area at a certain differential pressure (eg, 100 Pa) under laminar flow conditions is present as the fabric permeability in some air permeability tests, higher differential pressure (eg, 5200 Pa) of airflow might be required. 

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