CFD (acronym of Computational fluid Dynamics) helps promote Quality and Sustainability in the design and the operations of classified areas of pharmaceutical plants. Early at the design stage CFD allows to anticipate the real performance of HVAC systems in protecting critical locations in the manufacturing areas; zones with poor ventilation effectiveness, first-air disruption, backflow from dirtiest spaces, etc., can be detected in advance, reducing risk of contamination and thus improving quality and robustness of plants. CFD allows to introduce science rather than “magic numbers” or “rule of thumb” in the design. Moreover, CFD output help optimize HVAC systems, reducing their energy consumption and carbon footprint. In the same time CFD can support the C.C.S. and conscious and science-based decisions, in a QRM perspective.