EU. The EU guidance document “Manufacture of Sterile Medicinal Products” (3) provides the following site selection guidance: “18. Where aseptic operations are performed monitoring should be frequent using methods such as settle plates, volumetric air, and surface sampling (e.g., swabs and contact plates). Sampling methods used in operation should not interfere with zone protection.” USP. Similarly, the following guidance in the proposed revision to United States Pharmacopeia (USP) chapter (9) is of general interest: “Microbiological sampling sites are best selected when human activity during manufacturing operations are considered. Careful observation and mapping of a clean room during the qualification phase can provide information concerning the movement and positioning of personnel within these rooms. Such observation can also yield important information about the most frequently conducted manipulations and interventions.