Published on 05/12/2025
How to Perform Smoke Studies for Unidirectional and Turbulent Airflow in Pharma Cleanrooms
Smoke studies — also known as airflow visualization studies — are essential in pharmaceutical HVAC validation, particularly for sterile and aseptic processing environments. They offer visual confirmation of airflow patterns, directionality, and cleanliness zone separation. These studies help verify that critical areas are protected by unidirectional airflow, preventing contamination from operators, equipment, and facility design anomalies.
Conducting smoke studies correctly and interpreting their outcomes according to regulatory expectations from FDA, EMA, and Annex 1 (2022 update) is crucial for maintaining GMP compliance and data integrity.
1. Regulatory Expectations for Smoke Studies
The need for smoke studies is clearly outlined in international guidelines:
- EU GMP Annex 1 (2022): Requires documented evidence of unidirectional airflow protection in Grade A/B zones.
- ISO 14644-3: Recommends airflow visualization as part of operational qualification (OQ).
- FDA Guidance for Sterile Drug Products (2004): Emphasizes smoke studies in media fills and line setup validation.
These guidelines mandate not just performance of the test, but complete documentation, justification of conditions, and visual evidence like video footage.
2. Purpose of Airflow Visualization Studies
Smoke studies serve the following purposes:
- Verify unidirectional (laminar) flow in Grade A
Regulators expect a scientific rationale behind each study, clear execution steps, and risk-based interpretation of results.
3. Equipment and Materials Required
- Smoke Generator: Glycerin-based or glycol-based type, validated for use in cleanrooms
- Camera: High-definition video camera or CCTV system
- Tripod/adjustable stand: For consistent angle of recording
- Lighting: To avoid glare and ensure smoke contrast visibility
- Layout drawing: For mapping test points and documenting airflow direction
Ensure smoke is non-toxic, non-residual, and will not trigger fire detection systems. Safety precautions and cleaning procedures post-study must be in place.
4. Test Planning and Protocol Development
A smoke study protocol should be prepared before execution, including the following:
- Test objective and scope (e.g., Grade A LAF, pass boxes, airlocks)
- Location map with positions of equipment, operator, smoke source
- Airflow velocity and directionality criteria
- Recording method and video naming convention
- Acceptance criteria for unidirectional and turbulent flow
- Number of repetitions (minimum 3 for reproducibility)
The test plan should be approved by QA, HVAC validation, and production teams before execution.
5. Execution of Unidirectional Flow Smoke Study
This study is performed in Grade A areas (e.g., under LAF hoods, RABS, isolators).
- Place smoke generator at the filter face or inlet of airflow
- Generate smoke and record the flow path using the camera
- Observe and document whether smoke moves smoothly in one direction, sweeping away from the critical zone
- Repeat with equipment, materials, and operators in place (dynamic condition)
- Document any areas where smoke stagnates, curls, or reverses
Acceptance Criteria:
- Smoke must descend in parallel layers without turbulence
- No reverse or stagnant flow in critical zones
- Airflow should push away any potential contamination source
6. Execution of Turbulent Flow Smoke Study
This is relevant for Grade B/C/D areas and assesses general airflow patterns.
- Generate smoke at critical equipment height, operator level, and doorways
- Record smoke dispersion, swirl, or dead zones
- Identify areas with delayed air extraction or re-entrainment risks
Such studies help refine HVAC grille placement, air change rates, and operator movement zones.
7. Interpretation of Results and Documentation
Each smoke study must be accompanied by:
- Test Report: Detailing conditions, observations, and deviation (if any)
- Annotated Screenshots: With arrows showing smoke movement
- Video Recordings: Numbered and stored with metadata
- Observation Summary Table
| Test Area | Flow Type | Condition | Observation | Result |
|---|---|---|---|---|
| LAF Hood 1 | Unidirectional | Dynamic | Parallel flow, no turbulence | Pass |
| Pass Box Exit | Turbulent | Static | Swirl near corner grill | Requires CAPA |
8. Requalification and Frequency
Smoke studies must be repeated:
- During HVAC OQ and PQ
- Annually or biennially depending on classification
- After HVAC modifications or filter replacements
- During media fill setup validations
Study outcomes must be part of cleanroom qualification packages and must align with stability-sensitive zones as applicable.
9. Common Pitfalls and Regulatory Observations
- Smoke not visible due to poor lighting or dilution
- Unclear video angles or incomplete coverage
- No documentation of acceptance criteria
- Failure to study operator interventions during dynamic conditions
- No linkage to HVAC velocity or pressure differential records
FDA and EMA inspectors frequently request unedited footage and rationale for test locations — anticipate this during audits.
10. Integration with Other Validation Studies
Smoke studies should be linked to:
- HVAC OQ/PQ Reports
- Annex 1 Aseptic Processing Risk Assessments
- Air velocity test results
- HEPA filter integrity test records
- Media fill qualification
They serve as visual proof of contamination control strategy and should be referenced in the Validation Master Plan (VMP).
Conclusion
Smoke studies are more than just visual demos — they are a GMP-mandated, regulatory-inspectable validation step. When properly executed, documented, and interpreted, they provide strong assurance that cleanroom airflow is sufficient to maintain asepsis. QA, HVAC validation teams, and production personnel must collaborate to ensure these studies are technically sound, well recorded, and compliant with Annex 1 and ISO standards.
For SOP templates, smoke study protocols, and training aids, explore PharmaValidation.in.