Barrier systems: obstacles to contamination

Barrier is a generic term used to define any physical obstacle to contamination. The Category of PBSs (Protective Barrier Systems) can include any kind of protection apparatus like curtains of the clean room, biosafety cabinets, goggles, gloves, face shields and also isolators. What is usually not fully clear is that all these systems offer different degrees of protection (i.e. lower than isolator): pity that they are often used as synonimous!  An Isolator is a barrier, but a barrier isn’t necessarily an Isolator…

The arguments to consider when a technical solution  has to be choosen are the following:

  • Level of Toxicity of the product: the higher is the toxicity, the higher the barrier level. The Operator Exposure Level (OEL) of the potent compound expressed in mg/m3, µg/m3 or ng/m3 has to be considered
  • Quantity of product to be handled: increasing the quantity of product to handle, barrier level has to be increased
  • Level of Automation: manual vs. semi-automatic or fully automated procedures. if the process is fully automated , the presence of the operator all the time is not needed, this reduces the operator exposure to the toxic product
  • Level of Isolation: e.g. the possibility or not to fully isolate the process and/or the equipment. Not always the equipment needed in the process are ready to be fully isolated, or for some reasons a fully isolated system will complicate drastically the process. In the picture below there is an example of a tablet counting and a bottle filler machine (always for tablets) inside a “containment cabinet” (barrier).
    In this system there are four open doors:

    • Empty bottle inlet
    • Caps inlet
    • Foam inlet (small piece of foam to be introduced in the bottles after the tablets)
    • Filled and sealed bottle outlet

Example off "open isolator"

The cabinet cannot be considered a real Isolator (that must be fully closed), in any case the operator protection is ensured by the air flow. During the machine validation, using a tracer (smoke) and anemometers, it is possible to demonstrate that air can enter from the 4 foreseen openings only. NO air and than NO contamination is escaping. This is an example of Open Isolator: the process and transfer are highly isolated. The typical application is for production process which foresee small openings for exiting of bottles or vials.

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