Contaminant exposure in a pharmacy cleanroom with mixing ventilation: Impact of air-change rates

Ventilation is one of the primary strategies for controlling the contaminant exposure in a room. However, a lack of understanding in ventilation can lead to misinformation in estimating contaminant exposure. This includes the challenge of determining an appropriate ventilation flow rate (air changes per hour, ACH) and the airflow patterns required to keep aerosol particle concentrations limited. The goal of this work package of the P3Venti program is to investigate the impact of different values of ACH on the efficiency of contaminant removal in a pharmacy cleanroom employing mixing ventilation. The analysis combines experiments and CFD simulations. First, the CFD results of velocity magnitude, temperature, and particle concentration are validated with experimental data for the specific room. Next, the impact of ACH (i.e. 1.5, 3, 6, 10, 20, 40 h-1) on the distributions of velocity magnitude, temperature, and particle concentration is systematically analyzed. The results show that the buoyancy effect is significant at low ACH values, whereas the mixing effect becomes dominant at high ACH values. As ACH increases, the index of concentration reduction increases from approximately 48.5% to 96.5%, with most significant effects when ACH increases from 1.5 to 10 h-1. Similar follow-up research will be conducted for classrooms and general rooms in, e.g., long-term care facilities.