Reduced Access Barrier Systems – RABS


Reduced Access Barrier Systems – RABS

We have recently designed a facility for sterile products - the liquid filling of vials and subsequent freeze drying.  Initially we started with the assumption that we would use an isolated line.  However, the client, a generic manufacturer, was very concerned that the line should be flexible and easy to adjust for the wide variety of products and container sizes.  He wanted to use a closed RABS system.
So we ended doing a great deal of research on RABS.  The term ‘RABS’ covers a wide range of engineering options.  Offers from vendor ranged from beautifully engineered isolators with added doors at a price greater than an isolator to very ‘simple introduction level RABS’ at a price an order of magnitude less.

The threat – people

People - the danger
People are a significant of cause of contamination in cleanrooms.  They shed skin together with the bacteria on those flakes of skin, fungal spores and exhale bacteria and virus’.  People and clean operations do not mix.  So the basic idea of a RABS is to add a screen with glove ports to act as a barrier to keep people away from the process.  Hence the name Restricted Access Barrier.


The basic concept is to place a screen between the person and the sterile process.  To allow access the screen has glove ports.  That’s it.


A RABS consist of a screen, usually rigid and transparent with glove ports for access to the process.

The RABS is always associated with some form of airflow control, usually with a laminar flow.  The laminar flow and the RABS are often engineered as one piece. .  There  is a large variation in the quality, complexity and engineering quality of RABS – at one end of the spectrum they are simple screens with glove ports, at the other they are in effect isolators with opening doors that, once closed, are airtight enough to allow VHP sanitisation.

ISPE published a paper in 2005 to bring some definition to the subject.

 RABS are often described by  whether the enclosure is closed or not and by the way the airflow is engineered using teh following terms:

Open RABS – where the laminar airflow discharges into the room,
Closed RABS – where the laminar airflow is enclosed by the RABS and does not discharge into the room.  Here there has to be a return airflow contained within the isolator, and then:
Passive RABS – where the laminar airflow is provided elsewhere, usually in the ceiling of the room,
Active RABS – which has equipment to provide its own airflow.

Open, Active RABS photograph

Open Active RABS diagram


Where the RABS forms a complete enclosure round the equipment then openings (with doors) are provided to allow setting up of the equipment, its sanitisation and dismantling after use.

These doors are kept closed after sanitisation and during operation to maintain the laminar airflow and quality of air in the interior.  Opening the door causes the collapse of these conditions inside the RABS and is considered
Sanitisation is generally by manual means using alcohol sprays.  If vapour phase hydrogen-peroxide were used, as is common in isolators, then the RABS has to be closed and also vapour proof.  This requires a high quality of engineering.
In sterile processing contact parts have to be bought to the machine, passed through the barrier without disturbing the interior air quality and aseptically assembled.  Typically some form of airlock and additional laminar airflow outside the RABS is required.

Components have to get from outside to the inside of the RABS.  The arrangement for doing this can be complex.

Similarly the addition of sterile components to the line needs similar arrangements.
Lastly since the RABS is not sealed from the room the background environment of the room has to be a grade C or B.  This can complicate the arrangements of equipment and rooms considerably and creates greater initial and running costs

Pro & Con


  • As a RABS has access doors that can be opened it is easier to set up than an isolator.  
  • It is thought to be more flexible in use and suitable for multiple products and container sizes, especially if these are unknown at the time of design.


  • VHP sterilisation is generally not possible
  • More complex arrangement of rooms as background environment is of a higher standard.
  • RABS do not provide containment.  So unless they are closed and airtight they should not be used for potent products and dangerous pathogens without additional precautions.
Last Modified: Saturday 10 September 2016 06:09

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