The provisions for the qualification of purity zones in the manufacture of sterile medicinal products are set out in the current Annex 1. A crucial part of this qualification process includes the application of the classification according to EN ISO 14644 in order to ensure that measurements are carried out in compliance with the standard. Particular attention is paid to the measures from the contamination control strategy. In order to meet the requirements of Annex 1, the measurement intervals are optimised by applying risk-based approaches. Critical parameters are given special attention, while monitoring frequencies are reduced for less critical areas. This approach enables a targeted reduction in effort without jeopardising the quality of the measurement data. In addition, shorter test intervals for requalification and a clear distinction between qualification and monitoring must be taken into account. These specifications result in corresponding recommendations for action for the essential cleanroom measurements, which should serve as support for GMP-compliant and efficient cleanroom measurement technology.