Ventilation and Filtration Tradeoffs for Increasing Building Protection from Outdoor Aerosols

Outdoor pollutants, such as industrial chemicals, aerosols, and smoke, can pose acute threats to building occupants. The degree of protection provided by the building depends on many variable building characteristics, and decision-makers must develop planning actions in light of these broad unknowns. In this work, we propose to map the tradeoffs between building design, building operation, and the protection offered to occupants from pollutants of outdoor origin. Specifically, we compute and show the interplay between building characteristics (e.g., filter efficiency, envelope leakage), release conditions (e.g., distance from the building), and ventilation strategies (including pressurization and recirculation filtration). Our results suggest that building protection factors can vary by orders of magnitude. Counter-intuitively, moderate positive pressurization reduces peak concentrations by ~30%, while aggressive pressurization (60% return flow) may double indoor concentrations. HEPA filters achieve ~70% peak reduction. Combined strategies produce synergistic effects. Finally, we develop a graphical nomogram to help present the interplay between small changes in building operation and occupant safety.