Editorial | Open Access | Published 2nd of July 2026

GUEST EDITORIAL: The Different Risk Profiles of Isolators and RABS.

Author: James Drinkwater. Ex-Chairman and Honorary member of the PHSS: Pharmaceutical and Healthcare Sciences Society plus Head of GMP compliance for Franz Ziel GmbH, partner of Koerber.

Past research with ‘Body box’ studies demonstrated gowned operators, in Grade B gowning, generate airborne contamination including clinically significant micro-carrying-particles; MCPs. Following QRM principles, re-enforced in the revision of ICHQ9(R1) guidance the risk mitigation of ‘People and Process’ separation was encouraged in the revised Annex 1, 2022. Barrier separation technology (Pharmaceutical Isolators and RABS: Restricted Access Barrier Systems), Closed systems and use of technologies that mitigate risks of the ‘Human factor’ were encouraged. Human commensal contamination and human error are mitigated by reduced operator interactions into and within barrier systems plus use of automation and robotics that provide repeatable control.

In principle within Isolator and RABS it is possible to separate operators from established Grade A processing environments but in reality, Isolators and RABS have a very different risk profile and in this article the risk profiles are compared.

Open RABS filling lyophilised products, Closed RABS with VHP filling Ophthalmic products

Isolators with integrated automation for Aseptic manufacturing Filling of vials.

One of the main challenges and contamination risks for barrier technologies are at open barrier door set-up and introduction of sterilised in-direct product contact parts and for RABS, a rare justified open barrier door intervention during Aseptic manufacturing production.

Comparison of risk profiles between Isolators and RABS

One of the main variances in risk profiles is the set-up of sterilised (out-of-place) indirect product contacts parts into the barrier system. In Open RABS Grade A conditions are established before sterilised indirect product contact parts are installed and in Isolators such parts are installed before Grade A conditions are established, typically via automated VHP/vH2O2 bio-decontamination.

Also following the establishment of Grade A conditions within Isolators it is not permitted to open the barrier doors during aseptic manufacturing under any circumstances. However, in the past for RABS a rare open barrier door intervention could be justified with supporting risk assessments, protective airflow visualisation qualifications, APS qualification and supporting environmental monitoring that indicate the state of control is not compromised.

Following the revision and implementations of Annex 1; EU GMP, PICS and WHO together with revision of ICHQ9(R1) QRM there is more scrutiny on RABS and regulatory expectation now considers with the associated risks and ability to mitigate risks from operator interventions then Open barrier door interventions during aseptic manufacturing are not considered possible to justify and doors should remain closed during aseptic manufacturing production operations.

Further there is a lot more scrutiny on Open Barrier door interventions during set-up of sterilised in-direct product contact parts into RABS barriers. This does not mean there are no open questions or risks to mitigate in Isolator set-up of in-direct product contact parts, so scrutiny and discussion is required on both RABS and Isolators on what is considered GMP, best practice following QRM principles.

Set Up of Isolators

There are several questions and points to consider at Set-up of Isolators when installing sterilised in-direct product contact surfaces, Consider the following Questions and Answers:

Q1. Can absolute sterility be assured of in-direct product contact parts from transfer from an Autoclave Moist heat steriliser to and into an Isolator with Grade C surround?

Q2. How are sterilised In-direct product contact parts e.g. Stopper bowl, protected from contamination at transfer from an Autoclave to Filling Isolator?

Q3. What GMP grades apply at installation of the Stopper bowl into the Isolator via an open Barrier door?

Q4. What bioburden control measures apply, how are they qualified and how is protective wrapping removal managed during the parts installation process and for VHP bio-decontamination?

Q5. What monitoring is applied at Set-up inside the Isolator, in the Cleanroom and personnel monitoring?

Q6. Are Airflow Smoke studies required at Set-Up, if so, what?

A1. Can absolute sterility be assured of in-direct product contact parts from transfer from an Autoclave Moist heat steriliser to and into an Isolator with Grade C surround?

It is not possible to assure sterility is maintained after offload from a steriliser through transfer of GMP grades into the Grade C filling Cleanroom and outward installation in the Isolator barrier with entry via an open barrier door and before Grade A is established following subsequent VHP/vH202 bio-decontamination. There are just too many challenges to make that claim, whether the intent is to maintain sterility or not. In this case for Isolators there is the supporting process of the automated 6log sporicidal VHP/vH202 bio-decontamination process so there is the opportunity to re-establish surface sterility under certain conditions.

Those conditions include surface suitability including cleanability for a qualified VHP/vH202 bio-decontamination treatment and low bioburden as the challenge to the high-level efficacy of the bio-decontamination process, such that orders of overkill apply. The PHSS Clarity of GMP Guidance no.2; Assurance of sterility of In-direct Product contacts parts for Isolator applications sets out the requirements and bioburden control measures that include a 10CFU limit of bio-burden after installation is complete and before the VHP/vH202 bio-decontamination cycle.

A2. How are sterilised In-direct product contact parts e.g. Stopper bowl, protected from contamination at transfer from an Autoclave to Filling Isolator?

A minimum of two layers of protective wrapping, typically Tyvek®, is required during the Moist heat sterilisation process to protect at offload and during GMP grade transfers to the Filling line. An important point is the primary protection (last protective layer to be removed) covers the in-direct product contact surfaces e.g. inside a stopper bowl or chute stopper contact surface whilst leaving the underside exposed for mechanical connection to the Filling machine during the installation process. The secondary wrapping (bag) should be a complete over wrap. This secondary wrap should be removed at the Isolator door opening just before the primary wrapped parts enter the Isolator. At this process step protective airflow in the Isolator applies, operators have additional gowning (e.g. face mask, goggles) and EM applies. Trained operators following good aseptic technique are required to assure bio-burden control is maintained.

A3. What GMP grades apply at installation of the Stopper bowl into the Isolator via an open Barrier door?

For an Isolator that has this open barrier door set-up a Grade C surround is required (consistent with the Annex 1 requirement of Grade C for Open system Isolators). At this stage the environment within the Isolator is not Grade A as the VHP/vH202 bio-decontamination process is yet to be started. However the conditions in the Isolator are not expected to be Grade C, as the surrounding Cleanroom as a lower level of particulate and bioburden control is required at in-direct product contact part installation. During installation particulate levels of control within the Isolator should achieve Grade A, not to exceed levels, over and around the in-direct product contact parts. Within the Isolator and on non-contact parts of the process machinery Grade C levels of microbial contamination would apply that are later subjected to 6log sporicidal reduction from the VHP/vH202 Bio-decontamination process. Although Grade C limits are still a relatively low bioburden for the bio-decontamination process special lower bioburden control (<10CFU) is applied to the indirect product contact surfaces to assure surface sterility is achieved after the bio-decontamination process and implementation of bioburden control measures achieve and meet the target bioburden qualification level.

A4. What bioburden control measures apply, how are they qualified and how is protective wrapping removal managed during the parts installation process and for VHP/vH202 bio-decontamination?

The set bioburden control level of not to exceed or equal to10 CFUs on in-direct product contact surfaces requires a bio-burden qualification study that includes all the prerequisite of completing all the material transfer steps from Autoclave offload, through GMP Grade transfers and installation into place within the Isolator barrier. In the final step, before VHP/vH202 bio-decontamination, the primary protective covering is removed, and a bioburden (swabbing) study is completed. Once the bioburden qualification study is complete routine EM: Environmental monitoring applies with the in-direct (together with direct) critical surfaces sampled at end of batch to confirm Grade A conditions remained through production with 0 CFU recovery. The final primary wrap-cover should not be removed with the Isolator barrier door closed and it is considered best practice to remove the primary wrap-cover before the VHP/vH202 process. The justification for wrap-cover removal before the bio-decontamination cycle is that it is better to exposed the critical surfaces to the full process efficacy of the VHP/vH202 process as with the Tyvek® in-place VHP/vH202 distribution into the bowl is compromised, taping or strap attachment may add to the VHP/ vH202 penetration challenge, Aeration is be compromised as H202 molecule combine (via hydrogen bonding) under the Tyvek® and do not readily pass back on in Aeration.

In addition, the Warp-cover removal and waste removal process (typically via RTP waste port) is a particle generating activity so better completed ahead of establishing Grade A.

A5. What monitoring is applied at Set-up inside the Isolator, in the Cleanroom and personnel monitoring?

With the focus on air cleanliness (HEPA filtered protective airflow) over and around the In-direct product contact surfaces particulate counting with Grade A not to exceed limits should be completed adjacent in risk-based locations to the critical parts e.g. stopper bowl during the open-door installation process. However, during the installation process the particle counting Alert levels should be characterised for this state of control in variance to Alert levels that apply in Aseptic manufacturing with the barrier doors closed. As the focus on bioburden is for the in-direct product contact surfaces with associated bioburden qualification at this process step no addition EM for viable monitoring should be required inside the barrier ahead of the bio-decontamination cycle.

Where viable EM monitoring is required in set-up is at the risk-interface of the open barrier door, the operator and secondary protective wrap-cover removal. The requirement here is Grade C conditions with an assessment of controlling to characterised Alert levels. There are a number of bioburden control measures that apply at this process point and any breach of Alert levels of Grade C comprise is considered a risk escalation that needs review and possibly investigation. Monitoring at the Isolator—Cleanroom interface also provides Grade C filling session monitoring data that otherwise may be weekly or fortnightly as a routine.

A6. Are Airflow Smoke studies required at Set-Up, if so, what?

Yes, airflow visualisation studies are required in set-up alongside the other Airflow visualisation studies required for the barrier and filling process in-operation for Annex 1 compliance. The key point to consider here is the smoke studies should focus on protective airflows over and around the in-direct product contact surfaces and through the installation procedure. Outside and around in-direct product contact surfaces, with the barrier door open that may (likelihood) be turbulences and exchanges with the Grade C surround with the barrier door open. The protective airflow should not be compared with that of RABS that has an additional over-door L-UDAF protection and airflow protection is required to prevent compromise of Grade A inside the RABS with the barrier door open (the significant challenge to RABS).

RABS Set-Up and Open barrier door interventions

There are several questions and points to consider at Set-up of RABS when installing sterilised in-direct product contact parts and during open barrier door interventions during Aseptic manufacturing, Consider the following Questions and Answers:

Q1. How are sterilised In-direct product contact parts e.g. Stopper bowl, protected from contamination at transfer from an Autoclave to Filling RABS in Grade B surround?

Q2. Can sterilised parts enter for installation into RABS via an open barrier door?

Q3. What GMP grade applies under the overhead (LAF) L-UDAF of the open barrier door at open door intervention into RABS?

Q4. How is protective wrapping removal managed during the installation process into Grade A?

Q5. What monitoring is applied at Set-up inside the RABS and at open barrier door (rare) interventions during Aseptic manufacturing, in the Cleanroom and personnel monitoring?

Q6. Are Airflow Smoke studies required at Set-up and at open barrier interventions, is so, what?

A1. How are sterilised In-direct product contact parts e.g. Stopper bowl, protected from contamination at transfer from an Autoclave to Filling RABS in Grade B surround?

As with Isolators RABS indirect sterilised in-direct product contact parts require protective wrapping with a sterile barrier (Tyvek®) during the sterilisation process, at offload from the steriliser and through outward material transfers to the RABS filling Cleanroom. In this case the sterilised surfaces must remain sterile and not be compromised in any process handling steps and there is no ‘backup’ of a VHP/vH202 bio-decontamination process unless a Closed RABS with VHP/vH202 is specified.

At the final Material Airlock transfer into the Grade B filling room disinfection steps and possibly a packaging layer removal would apply. The packaging layer removal should still leave in-place the parts with the primary protective cover and secondary protective bag (full wrap) as the installation into the Open RABS has a much more critical objective being not the compromise the sterility of the sterilised parts and Grade A Aseptic manufacturing environment, that is re-established before sterilised parts enter the Open RABS.

A2. Can sterilised parts enter for installation into RABS via an open barrier door?

In the past some Open RABS have applied entry of sterilised in-direct product contact parts through an open barrier door with consideration the over-door L-UDAF and Grade B surround mitigate risks of compromise to the In-direct product contact parts and Grade A Aseptic manufacturing environment. APS qualification and supporting EM was also considered as justification for such an open intervention in processing step and during Aseptic manufacturing. With QRM requirements and Annex 1 principles that “Sterility cannot be assured by monitoring and testing alone” where focus is more on design and applied collective risk mitigations this open barrier door practice into Grade A is now under considerable scrutiny.

It is not unusual in RABS to have Grade A microbial recovery in EM results whilst in Isolators well designed, managed and operated Isolators have rare CFU recovery (for years of EM results).

Consideration is now given to entering in-direct product contact parts via a form of RABS barrier material transfer as a closed transfer to mitigate against need for open barrier door set-up. Best practice is also considered that after the final bio-decontamination step at set-up the barrier doors are closed and remain closed through Aseptic manufacturing production operations. Justifications why an open barrier door intervention is needed is likely to receive significant regulatory scrutiny even if considered a rare event.

A3. What GMP grade applies under the overhead (LAF) L-UDAF of the open barrier door at open door intervention into RABS?

The over-door L-UDAF (LAF unit) has the principal function of an airborne contamination control measure. Although the overhead HEPA filter will deliver Grade A cleanliness the complete open-zone under the L-UDAF cannot be considered Grade A. Once the operator steps under the L-UDAF the air cleanliness levels down grades to Grade B. Further the Grade B Cleanroom floor will be maintained as Grade B under the L-UDAF and over the complete Grade B surround floor.

The protective airflow from L-UDAF is not considered to be protective to Grade A environment inside the RABS alone and works in combination with Grade A air outflow from the RABS and onward flow to the Cleanroom floor level vents. Importantly no air that has passed over the Operator or from a lower level than the machine bed plate (below working height) should re-enter the Grade A environment inside the RABS. Airflow visualisation and qualifications are critical to assure protective airflow is in place, so Grade A is not compromised. The extent of operator intervention into an open barrier door can significantly challenge maintaining Grade A even with good aseptic technique performed in a procedure manipulation.

A4. How is protective wrapping removal managed during the installation process into Grade A?

As it is essential to maintain sterility of the Indirect product contact parts at introduction into the RABS Grade A environment, including the outer surfaces e.g. outside the Stopper bowl as these surfaces need to be maintained as Grade A technical and procedural controls are required. In these cases, the full primary and secondary protective wrapping remain in-place through the transfer process into the RABS and between mechanical installation on to the process machine the secondary cover-bag is removed leaving the final primary protection wrap-cover to be removed at the final step in the procedure with barrier doors closed and EM implemented.

If the installation of in-direct product contact parts is currently through an open barrier door (not best practice), this door must be covered fully with L-UDAF and procedural controls applied to remove the secondary protective wrapping at the entry into Grade A whilst the primary wrap-cover stay in-place until the barrier doors are closed.

A5. What monitoring is applied at Set-up inside the RABS and at open barrier door (rare) interventions during Aseptic manufacturing, in the Cleanroom and personnel monitoring?

At Set-up environmental monitoring is required but in the case of set-up EM limited to the location and immediate surround to the open barrier door, full line EM may not be justified (based on risk assessment). However, for a open (rare) barrier door intervention during Aseptic manufacturing full EM applies to the complete filling line, continuation of continuous viable and particulate monitoring through production operations.

Under the L-UDAF EM would be required at Grade B levels where the operator was completing the intervention. However, any open barrier door intervention into Grade A, either in set-up or during Aseptic manufacturing is a significant event and operator gowning monitoring is required on areas that entered/ interfaced with Grade A. Such monitoring should verify Grade A conditions were not compromised by the operator. Such operator monitoring should be completed immediately after the intervention under the L-UDAF and with ‘buddy’ support for EM plate handling and sampling.

A6. Are Airflow Smoke studies required at Set-up and during open barrier door interventions if so, what?

Yes, smoke studies are required at set-up and during open barrier door interventions. Airflow visualisation studies are required to verify the protective airflow pattern of air exiting the Grade A RABS, over the operator and onward to the Cleanroom floor level vent ducts.

Smoke studies are required through the complete procedure from opening barrier door (operator under L-UDAF) and closing the barrier door with door Grade A side surface disinfection as the last procedural step before closing the door.

Future and Trends

It is considered Open RABS that apply open barrier door interventions into Grade A will be considered as legacy designs e.g. O-RABS become obsolete RABS. If RABS remain as a barrier technology, then Closed RABS as a function of closed in set-up and operation after Grade A conditions are established will be come a requirement to follow the full principles of QRM.

In contrast Isolators are expected to become the primary barrier technology with a focus on improving Isolator design, operations, automated bio-decontamination systems, EM integration with digitalisation and improved integration of automation, including robotics.

With complex process machinery there remains the challenge of cleaning, disinfection and aerodynamic profiles that do not compromise First Air protection. For RABS the manual cleaning-disinfection step with such complex geometrics of processing machines remains a significant challenge both in terms of procedure and time to complete (production downtime). For Isolators cleanability is still a focus in design and procedural control but VHP/vH202 bio-decontamination properly integrated, qualified and controlled can be realised as a significant benefit in contamination control.

Closed RABS with VHP/vH2O2 can leverage some of the benefits and ways of working of Isolators to mitigate risks from RABS contamination control but in the context of closed system operation, including closed material transfers.

Sterilised part transfer into barrier systems will develop with closed material transfer technologies to mitigate risks of introduction into Grade A with open barrier door interventions.

Finally, one attribute of Isolators that is also significant is the containment potential, by design, to manage processing of hazardous and toxic products but for all products to better manage cross contamination control. Isolators have benefits over RABS that have limitations of containment with air overspill to the surrounding Cleanroom.