The impact of different air distribution and extraction strategies on the mitigation of airborne infection risk in classroom settings

• Air distribution and extraction strategies, including local exhaust, were studied • A higher airflow rate works best when the infector is near the exhaust. • Local exhaust performs better than a 25 % higher airflow rate with mixing. • Local exhaust systems showed consistent performance for all infector locations. • Canopy-based local exhausts achieved 45% contaminant reduction. Mitigating airborne infection risk in classrooms requires effective and reliable ventilation solutions. In this study, a full-scale classroom with eighteen pupils was modeled, and three possible locations of an infected person were considered. Mixing, wall-attached downward, and displacement supply systems were evaluated. Single- and multi-point ceiling exhausts (with one, two, or four outlets) were tested for mixing and wall-attached systems. A canopy-based local exhaust above the occupied zone was analyzed for wall-attached and displacement systems. Moreover, a mixing system scenario with 25% higher airflow (ACH) and a single exhaust was included for comparison. The validated CFD (computational fluid dynamics) model was utilized to analyze airflow patterns, contaminant concentrations, and infection probability. The results show that the performance of high airflow rate and multi-point extraction strategies improved conditions for only specific infector locations. Since the infector’s location is unknown in practice, these solutions may not be considered robust. However, the occupant-focused canopy exhaust system performed consistently well for all simulated infector locations. In the best-case scenario, the canopy system with displacement ventilation reduced the average contaminant concentration in the occupied zone by approximately 45% compared to the mixing system with a single exhaust. It also reduced the infection risk more effectively than other strategies, allowing at most two occupants to be in the high-risk category. The findings suggest that targeted local extraction is a more reliable and effective approach for minimizing the risk of airborne infection, offering a consistent solution regardless of the infector’s location.