Weekly tip: Yitai Jingke said today that the airflow organization in a clean environment has a certain impact on the environment. How to verify it? What are the operating methods, standards, and procedures?

CFR-V airflow pattern detector, brand: etiedt, a new product of Suzhou Yitai Environmental Technology Co., Ltd. It has a large atomization capacity, LCD display, multiple operation modes, simple operation, and easy maintenance.

Testing and Validation of Cleanroom Airflow Organization: Methods, Standards, and Procedures

The core function of a clean room is to control the concentration of suspended particles in the air, and the achievement of this goal largely depends on the specific and controlled airflow organization within it. Reasonable airflow organization can effectively suppress and eliminate pollutants, ensuring that critical process areas achieve the required cleanliness level. Therefore, scientific and standardized testing and verification of airflow organization is an important part of clean room acceptance, regular monitoring, and fault diagnosis.

1、 Why is airflow organization so important?

Airflow organization mainly affects the following aspects of clean environment:

1. 1.

   Pollutant removal efficiencyThe direction, velocity, and uniformity of the airflow determine whether it can quickly remove and discharge pollutants generated internally (such as particles emitted by personnel and equipment) to prevent cross contamination.

   
   

2. 2.

   Cleanliness maintenanceIn a unidirectional flow cleanroom, uniform and parallel airflow acts like a "piston" to continuously clean the workspace and maintain high cleanliness. In non unidirectional flow cleanrooms, the dilution and mixing of airflow are crucial.

   
   

3. 3.

   Temperature and humidity uniformityThe organization of airflow affects the degree of mixing of indoor air, thereby affecting the uniformity of temperature and humidity distribution in the space.

   
   

4. 4.

   energy efficiencyOptimized airflow organization can reduce air supply and energy consumption while achieving the same level of cleanliness.

   
   

Therefore, detecting and verifying airflow organization is the core means of directly evaluating the self-cleaning ability of a clean room.

2、 Main items and methods of detection and verification

The detection and verification of clean room airflow organization usually includes the following key items:

1. Airflow direction test

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  purposeVisually confirm the approximate direction of the airflow, verify if it conforms to the design (such as vertical unidirectional flow, horizontal unidirectional flow, turbulent flow), and check for dead corners, eddies, or backflow.

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  method：

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  Tracer line methodUsing lightweight silk thread (such as nylon thread, tobacco) or thin film strips, fix them on the measuring rod, place them at the position to be measured, and observe their direction of movement. This method has certain limitations.

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  Tracer methodAir flow pattern detector or specific smoke generator, using dry ice (producing white CO ₂ mist) to release visible smoke upstream of the air flow, observing the flow path and diffusion of smoke. This is the most intuitive and effective method. The advantages of the CRF-V airflow pattern detector are that it uses pure water as the medium, which will not pollute the clean environment. It has automatic replenishment and drainage functions, can test continuously for a long time, has a large amount of fog, is intuitive to observe, can be started remotely, reduces the influence of personnel on the airflow pattern, has LCD display, and easily understands the equipment operation data.

2. Wind speed and air volume testing

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  purposeEnsuring that the air supply meets the design requirements is the basis for calculating air exchange rates and ensuring cleanliness.

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  method：

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  Wind speed testMainly used for one-way flow cleanrooms. Using a calibrated hot ball or impeller anemometer, measure the wind speed uniformly at a height below the high-efficiency air supply outlet or in the working area of vertical unidirectional flow (usually 0.8-1.2 meters above the ground), and calculate the average wind speed.

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  Airflow testingMainly used for non unidirectional flow cleanrooms. Measure the outlet air volume of the diffuser or high-efficiency air supply outlet directly using an air volume hood. If there is no wind hood, it can be calculated by measuring the cross-sectional wind speed of the air outlet (scanned with an anemometer) and multiplying it by the net area of the air outlet.

  
  

  
  

  

3. Airflow uniformity test

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  purposeEvaluate whether the airflow in a unidirectional clean room is parallel and uniform, and whether there are significant velocity gradients or directional deviations.

  
  

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  methodDivide multiple equally sized grids on the air supply surface and work area section, measure the wind speed and direction at each grid point (using anemometers and tracer lines), and calculate the average wind speed, standard deviation, or relative standard deviation (non-uniformity).

  
  

4. Recovery capability test (self purification time test)

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  purposeEvaluate the ability of a clean room to restore to the specified level of cleanliness after a brief period of contamination. This indirectly but comprehensively reflects the efficiency of airflow organization.

  
  

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  method：

  
  

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  Atmospheric dust or smoke emission methodWhen smoking indoors (such as PAO, DOP, etc.), increase the particle counter reading to 100 or 1000 times the upper limit of cleanliness.

  
  

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  Stop smoking and start recording the changes in particle concentration over time.

  
  

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  calculateThe time required from the start of recording until the particle concentration drops to 100 times the cleanliness level is called the recovery time. Or calculate the time required for the concentration to decrease to 0.01% (100:1 decay).

  
  

5. Streamline parallelism test

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  purposeQuantitative evaluation of the degree of deviation of unidirectional airflow from parallel direction is a more accurate test of airflow direction.

  
  

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  methodUse a long enough filament and tie a heavy object at its end to make it perpendicular. Measure the wind speed vector at different positions (such as top, middle, and bottom) from the wire using an anemometer, and calculate the angle between the airflow direction and the theoretical vertical line.

  
  

3、 Main standards and specifications based on

There are a series of mature standards at home and abroad that provide detailed regulations for clean room testing, which must be followed when conducting testing and verification.

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  International Standard：

  
  

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  ISO 14644 seriesThis is the internationally recognized clean room standard. among whichISO 14644-3:2019Specially defined 'testing methods', detailing the testing procedures, instrument requirements, and data analysis methods for items such as airflow direction, wind speed, air volume, and recovery capability.

  
  

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  Domestic standards：

  
  

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  GB/T 25915.3-2021(Equivalent to ISO 14644-3:2019): "Cleanrooms and Related Controlled Environments Part 3: Testing Methods".

  
  

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  GB 50591-2010Code for Construction and Acceptance of Cleanrooms. This standard has more engineering guidance and clear regulations on the detection methods and acceptance standards of airflow, and is widely used in domestic engineering projects.

  
  

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  Industry Guide：

  
  

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  FDA Aseptic Process GuidelinesThere are strict requirements for the airflow pattern in pharmaceutical production cleanrooms, especially in sterile operating areas, emphasizing the need for visual research on airflow (Smoke Studies).

  
  

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  EU GMP Appendix 1High requirements have also been put forward for environmental monitoring of sterile drug production, including confirmation of airflow patterns.

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• Group StandardT/TPPA 0011-2025 Technical Specification for Airflow Visualization Testing of Unidirectional Flow Equipment in Pharmaceutical Industry Cleanrooms (Areas), Airflow Visualization Testing

4、 Standard Operating Procedure

The following is a typical operational framework for verifying the airflow organization in a clean room:

1. Preparation stage

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  document reviewRefer to the cleanroom design drawings and instructions to understand the type of airflow organization design (unidirectional/non unidirectional), the location of air supply/return ports, expected wind speed, and air volume.

  
  

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  Condition confirmationConfirm that the cleanroom is in a "completed" state, all service facilities are operating normally, and the air conditioning purification system has been running continuously for sufficient time (such as more than 24 hours) to reach a stable state. The temperature and humidity should be controlled within the specified range.

  
  

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  Instrument preparation and calibrationPrepare and calibrate all testing instruments (anemometer, air hood, smoke generator, particle counter, etc.) to ensure their accuracy meets standard requirements and is within the valid calibration period.

  
  

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  personnel trainingTesting personnel need to be familiar with standards, methods, and safety regulations.

  
  

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  site planningAccording to standards (such as ISO 14644-3) and design requirements, plan the location of test points on a plan or three-dimensional space.

  
  

2. Test execution phase

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  Airflow direction test：

  
  

1. 1.

   Release tracer in key process areas, around equipment, near door openings and return air vents.

   
   

2. 2.

   Observe and record the flow path of smoke from multiple perspectives (if necessary, video recording), paying special attention to whether there are eddies, stagnant areas, or flow errors.

   
   

3. 3.

   Record all observation results with icons or photos.

   
   

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  Wind speed/air volume test：

  
  

1. 1.

   wind speedFor a unidirectional flow clean room, divide the grid at a specified distance below each high-efficiency filter, measure the wind speed at each point, and calculate the average wind speed and uniformity.

   
   

2. 2.

   air volumeFor non unidirectional flow clean rooms, measure the outlet air volume of each air supply outlet, summarize the total air supply volume, and calculate the air exchange rate.

   
   

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  Recovery capability test：

  
  

1. 1.

   Set particle counters at key locations.

   
   

2. 2.

   Use smoke generators (such as PAO) that do not interfere with the cleanroom environment to emit smoke at concentrations far exceeding the baseline.

   
   

3. 3.

   Stop smoking and start the particle counter for continuous monitoring until the concentration returns to the required level.

   
   

4. 4.

   Record the curve of concentration over time and calculate the recovery time.

   
   

3. Data analysis and reporting phase

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  data organizationOrganize all raw measurement data into tables or charts.

  
  

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  result comparisonCompare the calculated average wind speed, air volume, recovery time, airflow uniformity, etc. with the design specifications or standard requirements (such as the recommended values in ISO 14644-3).

  
  

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  Conclusion judgmentDetermine whether the test results are qualified. If there are any non-conforming items, the reasons should be analyzed (such as air outlet blockage, filter leakage, unreasonable room layout, etc.), and corrective suggestions should be proposed.

  
  

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  Report PreparationProvide a formal testing report, which should include: testing purpose, standards, cleanroom status, instrument information, detailed testing steps, raw data, calculation results, conclusions, and attachments (such as photos and diagrams).

  
  

5、 Summary

Systematic testing and verification of the airflow organization in the clean room is the cornerstone to ensure that its performance meets design expectations and process requirements. It is not an isolated test, but a comprehensive evaluation that is interrelated and mutually confirmed with tests such as cleanliness, pressure difference, temperature and humidity. Strictly following international or national standards and implementing standardized operating procedures can not only ensure the quality of the cleanroom when it is put into use, but also provide scientific basis for long-term stable operation and efficient energy management in the future.

6、 Etiedt Yitai Jingke

Suzhou Yitai Environmental Technology Co., Ltd. is a leading manufacturer of intelligent detection instruments for clean environments, a domestic purification brand supplier, a high-quality purification service provider, and a professional enterprise providing complete solutions for intelligent monitoring instruments for clean micro environments. We specialize in intelligent dust particle counters, intelligent floating bacteria samplers, intelligent air volume hoods, aerosol generators, aerosol photometers, anemometers, temperature and humidity pressure difference testers, and remote particle counters