Maintaining the specified differential pressure between the cleanroom, the airlocks and their surroundings is essential. The controlled displacement flow ensures that the air quality of the cleaner area is not contaminated by cross-flows when openings are made in the cleanroom.

Differential pressure / displacement flow

In the case of openings in the cleanroom to adjacent areas of a different cleanroom class, the differential pressure measurement must be replaced by a check of the flow direction.

Testing the differential pressure and the displacement flow of air is used to monitor the capability of the cleanroom system. The specified differential pressure/displacement flow between the innermost and the next adjacent room must be maintained up to the last environment.

The differential pressure/displacement flow test should be carried out after the air flow velocity or air volume flow parameters have been met. For more information, see Air flow and determining the air exchange rate.

To avoid cross-contamination, pressure differences and displacement flows must be maintained and kept stable.


  • SN EN ISO 14644
  • VDI 2083 Sheet 3 Cleanroom technology – Measurement technology in cleanroom air
  • EU GMP Annex 1

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