Barrier Technologies From Clean Rooms to RABS and Isolators — Design Criteria for Barrier Technologies

In regulated markets — Europe, USA, Japan — barrier technologies are generally used in modern-day manufacturing and in bottling and sealing processes. There are many options for pharmaceutical companies, with decisions to be made on whether to use existing clean rooms with new or overhauled bottling and packaging systems or whether to invest in completely new processing technology.

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When processing pharmaceuticals which cannot be terminally sterilized in the container, the options range from the various RABS systems right through to isolator technology. There are currently a number of different RABS systems. Contamination control starts at “basic/low” and ends at “complex/high”. These completely enclosed systems boast the same minimal leakage rates as isolator systems. The decision as to which system is right for which application ultimately depends on a number of factors. There can be precious few hard and fast rules when it comes to decision-making scenarios as the objective requirements presuppose too many influencing variables. At the same time, each company has its own safety policies which can be reflected in its predilection for certain technologies.

Barrier Technologies: RABS and Isolators

As a general rule, a RABS is characterized by a rigid machine enclosure, safety locks on doors and sealed-in glove access. A RABS must always be installed in a class B clean room. Every RABS is fitted with an air circulation system. Pressure zones can be established, and the temperature can be controlled. Class A conditions are required within the RABS itself. In practice it is common to make the following further distinctions:

• Passive RABS

• Active RABS

• Active cRABS

The main differences lie in the design of the protective housing and the venting system. The passive RABS has no air circulation system of its own but is operated via the clean room venting system. The unidirectional displacement flow above the manufacturing process is provided by a laminar flow ceiling above the protective housing of the machine. The air is routed into the protective housing via this ceiling and then released back into the clean room in a controlled flow below the manufacturing process.

The active RABS has its own venting system in that the laminar flow unit is positioned directly on top of the protective housing and operates independently of the clean room ventilation system. The ambient air is drawn in from the surroundings by this laminar flow unit, passed through a HEPA filter, “laminarized”, routed above the manufacturing process, and — as with the passive RABS — is released back into the surroundings in the form of a controlled flow. In this case the room air circuit and the RABS circuit are separate. The active cRABS has its own venting system and, as a general rule, is completely independent of the room ventilation system. The exhaust air is returned either through external return air conduits or through double walls or double screens.

Operating Under Pressure

Due to the fact that it is a closed system, the active cRABS can be operated under pressure (product protection) or vacuum (human protection — not suitable for sterile processes). The process is completely enclosed with its own venting technology, which means that a manufacturing process can be subdivided into pressure zones as required. Here too, the air humidity can be controlled and regulated in addition to the temperature. A filling and sealing machine with isolator is a completely sealed and encapsulated system which can be operated in class D clean room conditions. The key feature of the isolator is the total segregation of the operator from the inner sterile zone. The individual process zones can also be separated from each other within the isolator. The products are then transported from one zone to another through “mouse holes”. It is then also possible to build in pressure cascades between the processing steps.

The air is always routed in one direction in the isolator, as in the RABS. Like the cRABS, however, the air passage is completely enclosed and independent of the surroundings. An isolator generally has its own ventilation or air conditioning unit so that the temperature and relative humidity in the process zone can be regulated. An isolator is required to have the facilities to enable the sterile transfer of products, primary packaging materials and components into the protected area. It must also be possible for automatic and reproducible bio-decontamination (sterilization) processes to be carried out with vaporized H₂O₂.

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