Laminar airflow unit

The greatest risk of contamination of a pharmaceutical product comes from its immediate environment. Additional protection from particulate and microbial contamination is therefore essential in both the filling area of the clean room and in the aseptic unit. This can be provided by a protective work station supplied with a unidirectional flow of filtered sterile air. Such a facility is known as a laminar airflow unit in which the displacement of air is either horizontal (i.e. from back to front) or vertical (i.e. from top to bottom) with a minimum homogenous airflow rate of 0.45 ms" at the working position. Thus, airborne contamination is not added to the work space and any generated by manipulations within that area is swept away by the laminar air currents. 

Workbenches, including laminar airflow units, and equipment, should be disinfected immediately before and after each work period. Equipment used should be of the simplest design possible commensurate with the operation being undertaken. 

Aseptic manipulations should be performed in the sterile air of a laminar airflow unit. Speed, accuracy and simplicity of movement, in accordance with a complete understanding of what is required, are essential features of a good aseptic technique. 

Verify that the laminar airflow units in class 100 areas are operational. Verify that the ventilation and air conditioning systems are operating in balance. 

Powder exhaust units, Laminar airflow units, Safety cabinets and Isolators... 

A Laminar airflow unit, also called laminar flow -cabinet, -closet, -hood or -bench is a general and rather non-specific term for an enclosed workbench, with a HEPA filtered laminar airflow inside. 

The operational aspects of maintenance and caUbration for safety cabinets are almost the same as for cross flow laminar airflow units (see Sect. 28.3.5). Additionally the inflow as protective barrier has to be measured. 

The fitting of limiting boundaries such as walls pros ides solutions similar to those of laminar airflow (LAP) units tir cabinets. An increase in the supply and exhaust supply rates provides a solution similar to ventilated booths (.see Section 10,. ). 

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. 

Airflow visualization (To verify required airflow patterns) All classes 24 months Tests to demonstrate airflows from clean to dirty areas do not cause cross-contamination uniformly from laminar flow units. Demonstrated by actual or videotaped smoke tests. In accordance with ISO 14644-3 Annex B7 ... 

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 terminal HEPA filtration module (TFM) is a self-contained HEPA filter and plenum unit (Fig. 11), which may be used to provide laminar or conventional airflow to a clean space, or may be dedicated as a LAF workstation.f The TFM is available with a 10 in. (optional 12 inch) collar for connection by a circular supply duct to a central air handling system (Fig. 5A) or as a free-standing, fully powered unit containing a motor and blower. It is normally installed in a... 

Figure 10.4 Airflow patterns for dispensing areas used for filling pharmaceuticals or toxic materials, (a) Conventional clean room with air circulation. Operated at positive pressure relative to atmoshere. (b) Room used to dispense toxic material with total air discharge. Operated at negative pressure relative to atmosphere, (c) Hybrid room. H, HEPA filter A, air circulation fans B, containment cabinet F, filling unit C, laminar flow air hood arrow, direction of air flow.

A laminar flow cabinet will continuously produce heat from the ventilators. If the exhaust airflow from the LAF unit is returned into the room (recirculation), the temperature in the room will rise and more room ventilation and cooling is necessary. Air exhaust to outside the room will give less heating of the room. 

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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