Cleanroom smoke studies are critical to assessing the airflow, cleanliness, and overall performance of controlled environments such as cleanrooms. Contamination control is essential for pharmaceuticals, biotechnology, electronics, and aerospace products. These studies help ensure that airflows are appropriately designed and maintained to minimize particle contamination and that airflow paths effectively remove contaminants.

Reasons Cleanroom Smoke Studies Are Required:

1.     Airflow Validation:

• Purpose: Smoke studies help verify that the cleanroom’s airflow system operates as intended, with airflow patterns supporting contamination control. This includes checking whether clean air is correctly directed to critical areas (such as sterile zones or regions where sensitive processes occur) and whether dirty air is efficiently removed from the cleanroom.
• Why It Matters: If the airflow is not aligned with the cleanroom design, contamination may not be adequately controlled, leading to potential product contamination or failure to meet regulatory cleanliness standards.

2.     Testing for Contaminant Migration:

• Purpose: Smoke studies allow operators to track airflow across the cleanroom and see how it might transport contaminants. By visualizing airflow with smoke, one can observe whether contamination might flow from lower cleanliness zones into areas that require higher levels of sterility or cleanliness.
• Why It Matters: Even with a well-designed cleanroom, unanticipated airflow patterns could allow contaminants to migrate into critical areas, risking the quality of products or experiments conducted in those zones.

3.     Monitoring Air Change Rates (ACH):

• Purpose: Air Change Rates (ACH) are crucial for maintaining cleanliness in the cleanroom. Smoke studies can help assess whether air changes per hour are adequate for the cleanroom’s classification and cleanliness requirements.
• Why It Matters: Insufficient air changes could result in particulate levels exceeding acceptable thresholds, jeopardizing product quality or safety. ACH must be regularly tested to meet the cleanroom classification standards (e.g., ISO 14644).

4.     HEPA Filter Efficiency:

• Purpose: HEPA filters are critical for trapping airborne particles, including microorganisms. Smoke studies provide a way to observe particle movement in the cleanroom and verify whether HEPA filters function as intended by capturing contaminants and preventing them from spreading.
• Why It Matters: If HEPA filters are not operating effectively or are damaged, contaminants may enter clean zones, which could contaminate sensitive products or processes.

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5.     Pressure Gradient Verification:

• Purpose: Cleanrooms are typically designed with specific pressure differentials to ensure that air flows from cleaner to dirtier zones, preventing contamination from migrating into critical areas. Smoke studies can visually demonstrate whether these pressure gradients are maintained.
• Why It Matters: Failure to maintain the proper pressure gradient can contaminate lower to higher cleanliness areas, compromising sterility and cleanliness standards in controlled environments.

6.     Leak Detection:

• Purpose: Leaks in the cleanroom envelope or the air distribution system can allow contaminated air from external sources to enter, compromising the cleanroom’s integrity. Smoke studies can help identify leaks in walls, doors, windows, or HVAC systems.
• Why It Matters: Leaks are a significant source of contamination ingress, particularly in environments where sterile conditions are crucial. Identifying and addressing leaks ensures the cleanroom environment remains effective in controlling contamination.

7.     Operational Adjustments:

• Purpose: After performing smoke studies, operators can assess areas where airflow patterns are less than ideal and make necessary operational adjustments. This could include repositioning air diffusers, adjusting the HVAC system, or redesigning cleanroom areas to improve airflow and contamination control.
• Why It Matters: By identifying inefficiencies or problematic airflow patterns, the overall cleanroom environment can be optimized for better contamination control, improving process reliability and product quality.

Step-by-Step Guide for Executing Cleanroom Smoke Studies

1.     Preparation and Planning

• Define Objectives:
  • The first step clearly defines the purpose of the smoke study. Are you verifying airflow patterns, checking filter integrity, assessing contamination control measures, or evaluating other aspects like air change rates or pressure gradients?
  • The objectives will dictate the approach and areas of focus for the study.
• Choose the Correct Smoke Method:
  • Cleanroom smoke studies can use visible smoke (e.g., smoke tubes or smoke generators) or tracer gases. Visible smoke is often preferred as it allows for real-time observation of airflow patterns. Tracer gases may be used when smoke is not ideal for a particular environment or when more precise measurement is required.
  • Smoke Tubes: These are small, easy-to-use devices that emit visible smoke when activated. They are commonly used for smaller studies or localized assessments.
  • Smoke Generators: These generate a continuous stream of visible smoke and are used for more comprehensive or larger-scale studies.
  • Tracer Gases: Tracer gases (like SF6 or nitrogen) may be used to control the study more precisely or evaluate gas dispersion in the cleanroom. These gases are less visible but can be monitored with specific sensors.
• Select the Right Tools and Equipment:
  • Smoke Tubes/Generators: To introduce visible smoke into the environment.
  • Anemometers: To measure airflow velocity.
  • Particle Counters: These measure the number of airborne particles before and after the test to assess how efficiently contamination is removed.
  • Airflow Visualization Equipment: Devices such as smoke cameras or digital systems to capture real-time airflow visualization.
  • Pressure Measuring Devices: These measure pressure gradients between different cleanroom areas.
  • Data Loggers record the study’s environmental conditions (temperature, humidity, and pressure).
• Identify Study Areas:
  • Define the specific areas to be studied based on the objectives. Common areas include:
    • Air supply points: To check the uniformity and direction of airflow.
    • Return air vents: Ensure airflow is properly circulating and contaminants are removed.
    • HEPA filters: To assess the efficiency of the filtration system.
    • Critical zones require the highest level of cleanliness (e.g., sterile zones in pharmaceutical clean rooms).

2.     Pre-Study Cleanroom Setup

• Ensure Cleanroom is in Operation:
  • The cleanroom should be running under normal conditions, with HVAC, lighting, and other equipment operating as they would during typical production.
  • This ensures that the study reflects real-world conditions.
• Ensure Stable Environment:
  • All systems (e.g., HVAC, lighting, and equipment) operate within standard specifications. Any sudden changes in conditions (e.g., HVAC malfunction or equipment shutdown) could affect airflow patterns and distort results.
• Verify Environmental Conditions:
  • Before starting, ensure that temperature, humidity, and pressure are within the acceptable range for the cleanroom classification.
  • Pressure differentials should be checked to ensure air flows from cleaner to dirtier areas and that any pressure-sensitive areas (e.g., negative pressure zones for sterile areas) function correctly.

3.     Smoke Study Execution

• Introduce Smoke:
  • Position the smoke source strategically based on your study objectives. For example, place the smoke near air supply diffusers to observe how air flows into the cleanroom, near exhaust vents to check air removal efficiency, or near HEPA filters to visualize particle capture.
  • Smoke tubes/generators should be activated using the method selected.
• Observe Flow Patterns:
  • Allow the smoke to rise and follow its movement. Pay attention to how the smoke interacts with the airflow:
    • Turbulence: Areas where smoke behaves unpredictably or chaotically.
    • Stagnant Areas: Regions where smoke lingers or fails to disperse, suggesting poor airflow or inadequate air changes.
    • Clean/Dirty Zones: Observe if smoke enters critical areas (e.g., sterile zones) where it should not be present.
• Take Measurements:
  • Measure airflow velocities using an anemometer to assess whether the airflow meets cleanroom specifications.
  • Measure pressure gradients to confirm the appropriate pressure differentials between cleanroom areas.
  • Particle Counters may be used to verify the effectiveness of airflow in reducing airborne particle levels.
• Record Findings:
  • Document observations such as smoke behavior (e.g., directions, speed, dispersion) in different cleanroom areas.
  • Note turbulent regions, stagnant zones, and any areas where smoke moves into undesired locations.
  • Record data from instruments (e.g., airflow velocities, pressure gradients, particle counts) to provide a quantitative assessment.

4.     Post-Study Analysis

• Evaluate Smoke Movement:
  • Analyze the movement of smoke concerning airflow patterns. Identify areas where airflow is insufficient or turbulent.
  • Insufficient airflow could indicate that more air changes per hour are needed or that the air supply/diffuser placement needs adjustment.
• Analyze Contaminant Migration:
  • Examine if the smoke (representing contamination) moved into critical or undesired zones, indicating possible weaknesses in contamination control systems.
  • Potential contamination migration into sterile or clean areas suggests adjusting airflow or pressure differentials.
• Corrective Actions:
  • If problems are detected, make necessary adjustments to the cleanroom:
    • Reposition air diffusers or adjust HVAC settings to improve airflow distribution.
    • Fix leaks in walls, doors, or HVAC systems that could allow contamination to ingress.
    • Adjust pressure differentials to maintain clean-to-dirty airflow.
    • Repair/Replace HEPA filters or airflow systems that are not performing as expected.

5.     Reporting

• Create a Detailed Report:
  • Include a comprehensive description of the study methodology, areas studied, and results.
  • Document observations of smoke behavior, airflow patterns, and any deviations from expected results.
  • Provide quantitative data from anemometers, particle counters, and pressure measurements.
  • Include visuals (images or videos) of the smoke patterns and airflow behavior, particularly around critical areas.
  • Outline any corrective actions taken or recommended to improve the cleanroom performance.
• Compliance and Review:
  • Ensure the final report meets the internal standard operating procedures (SOPs) and complies with external regulatory requirements (e.g., ISO 14644, FDA guidelines).
  • Quality assurance teams or regulatory bodies may need to review the report to confirm compliance and ensure the cleanroom operates within the required specifications.

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Regulatory Guidance References for Cleanroom Smoke Studies

1. ISO 14644-3:2019 – Cleanrooms and associated controlled environments – Part 3: Test methods
   • ISO 14644-3 provides standards and guidelines for testing cleanrooms, including airflow patterns and pressure differentials. Smoke studies are often used as part of the test methods outlined in this standard.
2. FDA 21 CFR Part 820 – Quality System Regulation (QSR)
   • The FDA’s regulations may require cleanroom studies as part of the overall qualification process for manufacturing environments, especially in pharmaceutical and medical device industries.
3. EU GMP Annex 1 – Manufacture of Sterile Medicinal Products
   • Annex 1 of the EU GMP guidelines emphasizes the need for environmental monitoring, airflow design, and validation of cleanrooms, which often includes smoke studies as part of the qualification process.
4. ISO 14644-1:2015 – Cleanrooms and associated controlled environments – Part 1: Classification of air cleanliness by particle concentration
   • While not directly focused on smoke studies, this standard helps define cleanroom cleanliness requirements. It explains why airflow studies and visualizations (such as smoke studies) are necessary.
5. ISO 14698-1:2003 – Cleanrooms and associated controlled environments – Biocontamination control – Part 1: General principles and methods
   • This standard addresses biocontamination control. While focused on microbiological aspects, it helps justify airflow studies and cleanroom monitoring as part of the overall contamination control strategy.
6. Guidelines from Industry-Specific Bodies:
   • GxP Guidelines: Good Manufacturing Practices (GMP), Good Laboratory Practices (GLP), and other GxP-related guidelines often require environmental qualification, which may include smoke studies.
   • ASHE (American Society for Healthcare Engineering) and SMACNA (Sheet Metal and Air Conditioning Contractors’ National Association) guide cleanroom design and validation, including airflow and smoke studies.

By following these guidelines and conducting regular smoke studies, you can ensure your cleanroom meets the necessary cleanliness, airflow, and contamination control standards.

Contact Us:

Contact GxP Cellators Consultants at for your cleanroom projects, including the execution of cleanroom smoke studies.