Effects of mask leakage characteristics on aerosol inhalability and deposition in the human nasal cavity

Frequent emergence of infectious respiratory diseases has highlighted the importance of effective respiratory protection against airborne particle exposure. However, imperfect mask fitting often leads to leakage at the mask–face interface, which significantly influence aerosol inhalability and deposition in the human airway. In this study, a coupled numerical model including the breathing zone, face mask, facial interface, and nasal cavity was developed. The model was used to investigate airflow leakage and the subsequent transport and deposition behavior of inhalable aerosols. Representative leakage scenarios were simulated to evaluate effects of leakage location, breathing intensity, and leakage area on particle transport behavior. Results show that leakage location strongly affects airflow organization and particle transport. Midline leakage produced symmetric flow and deposition in the nasal cavities, while cheek leakage induced pronounced asymmetric deposition. Even with leakage, mask wearing still reduces particle penetration into the deeper respiratory tract. Compared with the no-mask condition, particle penetration decreases by an average of 7.36%, with the largest reduction (13.8%) observed under chin leakage. Increasing breathing intensity enhanced particle inertia and promoted inertial impaction in the upstream nasal regions. As the inhalation rate increased to 60 l/min, the overall nasal deposition efficiency reached 90.6%. In contrast, leakage area mainly redistributed particle deposition locations within the nasal cavity while exerting a limited influence on overall deposition–penetration balance. The findings provided insights into aerosol inhalation exposure under mask leakage conditions. It aimed to improving respirator design and respiratory protection strategies.