Design of HEPA-filters above autoclaves and freeze-dryers.
In pharmaceutical manufacturing some processes and process equipment cause temperature differences relative to the surrounding air, e.g. sterilisation and freeze-drying processes. Generally there is a temperature difference when a door to such equipment is opened. This can cause a flow of room air through the opening, creating a contamination risk, especially when manual handling of material is performed in this area. To minimize this risk, a HEPA-filter unit should be installed above the opening to provide clean air and protect the opening. The airflow needed through the HEPA-filters depends mainly on the temperature difference between the chamber and the room and the size of the opening. The flow of clean air should be greater than that of the theoretically calculated flow in order to minimize contamination hazards. In this paper the theoretical relations are discussed and design criteria are presented in a simplified form with graphical representations. Results from a case study are described and the experimentally estimated air-flow values are compared with the theoretically calculated values.
Kungliga Tekniska Högskolan, Stockholm, Sweden.
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B
Ljungqvist
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B
Reinmüller
D004345:Drug Industry; D005374:Filtration / Q000295:instrumentation*; D005612:Freeze Drying; D013242:Sterilization; D013696:Temperature