The purpose of the airflow parallelism test is to show the actual airflow pattern throughout the unidirectional cleanroom. It can also be used to demonstrate the effects on airflow caused by equipment. This test should be performed after all airflow velocity and uniformity tests and room pressurization tests have been performed. Determining the airflow patterns within a room is performed using various mediums which include the following non-contaminating items; vapor source or streamers of thread or string.

INSTRUMENTATION AND EQUIPMENT

• Test Medium (non-contaminating items; carbon dioxide, glycol or other visible vapor source or streamers of thread or string).

• Support stand which will least affect the airflow in the test location aerodynamically, and will allow the positioning of the test medium at the specified location and height.

• Plumb bob or spirit level

• Measuring tape

• Pointer and stand

TEST PROCEDURES
 

• Divide the cleanroom into grids of equal area having dimensions of 3 m x 3 m (10 feet x 10 feet).

• Secure plumb line, spirit level, or straight edge as required. Mark the plumb line at 305 mm (12 inch) intervals.

• The distance from the plumb line to the streamer or vapor is determined at a distance of 915 mm and 1520 mm (36 and 60 inches) above the floor. The length of the plumb line should not exceed 1.2m (4 feet).

• Introduce the aerosol test medium using the support stand at the specified test grid location and height.

• The angle of deflection is then calculated based on the measured horizontal offset from true Vertical.

ACCEPTANCE

The angle of deflection should not be greater than 14° from center when measured higher than 915 mm (36 inches) above the floor.
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Reference links
https://www.google.co.in/amp/s/gowrimanoja.wordpress.com/2014/03/19/air-flow-velocity-and-uniformity-test-and-air-flow-parallelism-test/amp/
https://amcleanroombuild.com/news/the-4-elements-of-cleanroom-design-certification-and-maintenance-part-2/