In the production area, especially in areas for the manufacture of pharmaceuticals, it is the task of the companies manufacturing according to GMP to identify contamination risks in the course of production and to implement an effective contamination control strategy (CCS). In this context, cleaning and disinfection processes play a role in addition to the consideration of the manufacturing process, the spatial conditions, the personnel, and the associated personnel hygiene. In this context, European Norm (EN) methods for determining the effectiveness of disinfectants can be adapted for the validation of disinfectants in the GMP environment. In this way, the required proof of the efficacy of the disinfectants used on the in-house specific surfaces can be demonstrated in a systematic, application-related, and needs-based manner. This includes both the surfaces available on site and the in-house flora, i.e., the specific microorganisms detected at the production site.