Pharmaceutical cleanrooms depend on controlled airflow to protect exposed products, components and critical surfaces. In aseptic manufacturing, smoke studies help teams visualise airflow behaviour under defined operating conditions.
However, capturing a video of smoke movement is not enough. The observations must be assessed against predefined acceptance criteria to determine whether the airflow pattern provides the intended protection.
This article outlines a practical approach to reviewing airflow visualisation results in GMP cleanrooms.
- Define the Expected Airflow Behaviour
Before conducting a smoke study, identify what the test is intended to demonstrate.
The protocol should consider:
Cleanroom layout and equipment configuration
Critical process locations and exposed products
Intended airflow direction
Relevant operating conditions
Routine interventions and operator movements
Potential contamination pathways
The expected airflow behaviour should be clear enough for reviewers to compare actual observations with the predefined criteria.
- Capture Representative Operating Conditions
Airflow can change when operators interact with equipment or move materials through a critical area.
A study should therefore consider relevant operating conditions, rather than relying only on observations made in an unoccupied room.
Depending on the process, the protocol may include material transfer, equipment handling, component replacement and other representative interventions.
Video recordings should clearly show the test location, the activity being performed and the resulting smoke movement.
- Evaluate Airflow Observations Systematically
A structured review helps teams avoid relying on subjective impressions of whether airflow looks acceptable.
The following table summarises useful observation points.
Observation
What to assess
Airflow direction
Whether air moves in the intended direction
Product protection
Whether exposed products and critical surfaces receive appropriate protection
Turbulence and eddies
Whether local disturbances affect critical locations
Operator interventions
Whether activities disrupt the intended airflow pattern
Reversal or ingress
Whether air moves from less clean areas towards higher-grade areas
Smoke clearance
Whether slow-moving or stagnant patterns require further assessment
Not every visible disturbance represents a failure. Its significance depends on its location, duration, operating conditions and potential effect on product protection.
- Review Interventions and Local Disturbances
Operator movements and equipment arrangements can create local airflow disturbances.
For example, an intervention near an exposed product may influence the airflow pattern around that location. Reviewers should examine the video to understand whether the disturbance affects the intended protective airflow.
The assessment should record the observation, its location and the conditions under which it occurred. Where a potential contamination risk is identified, it should be evaluated and documented through the site's quality system.
- Establish Acceptance Criteria Before Execution
Acceptance criteria should be defined before the study begins. They should reflect the facility design, process requirements and contamination risks.
EU GMP Annex 1 addresses airflow visualisation and the need to demonstrate appropriate airflow protection in cleanrooms and critical areas. It does not establish one universal numerical pass/fail limit for every visible smoke pattern.
Manufacturers should therefore define and justify study-specific criteria through documented risk assessment and approved procedures.
- Maintain Traceable Study Records
A review is only useful when its conclusions can be traced back to the evidence.
Depending on the approved protocol, the study record may include:
Approved protocol and acceptance criteria
Test locations and operating conditions
Equipment configuration and relevant interventions
Smoke-generation details
Original video recordings
Annotated footage and observation logs
Assessment of observations against criteria
Deviations and investigations, where applicable
Review and approval records
Timestamps and location references can make it easier to connect a finding in the report with the corresponding video evidence.
- Distinguish Smoke Visualisation from Recovery Testing
Smoke visualisation and cleanroom recovery testing provide different types of evidence.
Smoke studies demonstrate visible airflow behaviour. They help teams understand airflow direction, local disturbances and the influence of interventions.
Recovery testing evaluates how quickly a cleanroom returns to a specified particle-cleanliness condition after a defined challenge.
Visible smoke clearance should not be treated as proof of particle recovery or restoration of the qualified cleanroom state.
Conclusion
A structured smoke study review connects airflow observations with predefined acceptance criteria and the protection required by the process.
By evaluating airflow direction, product protection, turbulence, interventions, potential ingress and supporting documentation, pharmaceutical teams can make more consistent assessments of cleanroom airflow behaviour.
The conclusions should always be based on the approved protocol, facility design and contamination-control requirements.
For a more detailed discussion of smoke study acceptance criteria and airflow risk assessment, see IncepBio's guide to smoke study acceptance criteria.
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