This VDI guideline essentially deals with particulate contamination. Chemical (molecular), biological and radiological surface contamination is not a specific issue in this guideline; the same holds true for process media. This guideline provides definitions of the terms compatibility with the required cleanliness and cleanroom compatibility and, based on these definitions, the lassification and procedures serving to establish the suitability of equipment and air-handling components for use in environments whose air cleanliness and other parameters are assessed in accordance with technical rules (see Figure 3). Furthermore, it describes the outgassing and electrostatic characteristics of equipment and air-handling components associated with controlled environments. Surface cleanliness and its classification are also within the scope of this guideline. The compatibility of a piece of equipment with the required cleanliness includes all contaminations relevant to the process. The measuring techniques described in this guideline, serving to assess the compatibility of equipment with the required cleanliness comprise cleanroom compatibility, surface particulate cleanliness, outgassing behaviour.