Airflow Direction Test or Visualization Test


The purpose of the Airflow Direction Test and visualization is to confirm that the airflow direction and its uniformity conform to the design and performance specifications.


  • Refer Annex I (Table 1: Minimum Instrumentation requirements)


General considerations:


The Airflow Direction Test and visualization can be performed by the following methods:

  1. Tracer Injection method:
  2. The test is carried out by observation or imaging of the behavior of tracer particles illuminated by high intensity light sources, and provides information about the direction and uniformity of airflow in installations.
  3. The tracer particles can be generated from materials such as de-ionized (DI) water, sprayed or chemically generated alcohol/glycol etc. The source should be carefully selected to avoid contamination of surfaces.
  4. The desired size of droplets should be considered when selecting the droplet generation method. Droplets should be large enough to be detected with the available image processing techniques, but not so large that gravitational or other effects will result in their motion diverging from that of the airflow being observed.
  5. Airflow visualization method by image processing technique:
  6. Processing particle image data derived from the method described in Point 2 above (Tracer Injection method) on video frames or films provide quantitative characteristics of airflow by way of two-dimensional air velocity vectors in the area. The processing technique requires a digital computer with suitable interfaces and the appropriate software. For greater spatial resolution, devices such as a laser light sources can be used.


  1. Generate and introduce a cloud of vapor at each area to be tested for direction of airflow
  2. Video shoot the direction of airflow
  3. Measure the offset distance and radial direction of the air flow


  1. In this test, if the angle of deflection of the airstream from perpendicular needs to be evaluated, then this angle of deflection should not be greater than 140.
  2. Readings in excess of 140 offset are a matter for agreement between the customer and the supplier.


By agreement between customer and supplier, the following information and data should be recorded:

  1. Type of tests, method of visualization and test conditions;
  2. Type designations of each measurement instrument and apparatus used and its calibration status;
  3. Visualization point locations;
  4. Images stored on photographs or video cassettes, or raw data for each measurement, in the case of the image processing technique or the measurement of velocity distributions, if specified;
  5. A plan of the exact location of all apparatus should accompany the flow visualization report;
  6. Occupancy state(s).

For More Article On SOP

  1. SOP For Airflow Velocity and Uniformity Test
  2. SOP For Temperature and Humidity Test
  3. SOP For Room Pressure Difference Test
  4. SOP For Installed Filter Leakage Test