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Updated: Jul 16, 2026

Safety Precautions and Operating Procedures in an (A)BSL-4 Laboratory: 3. Aerobiology
Published on: October 3, 2016
Loading and unloading of freeze-dryers: airborne contamination risks for aseptically manufactured sterile drug
Bengt Ljungqvist1, Berit Reinmüller
1Building Services Engineering, KTH, Stockholm, Sweden.
Abstract:
In pharmaceutical manufacturing, freeze-drying processes can be adversely affected by temperature differences relative to the surrounding air. Loading and unloading of freeze-dryers are performed either without or with temperature differences between the cleanroom and the chamber of the freeze-dryer. This operation 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 high-efficiency particulate air (HEPA) filter unit should be installed above the opening to provide clean air and protect the opening. Here the theoretical relationships are discussed and design criteria are presented.
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