Aerosol Deposition on Facial Masks in an Open Environment during Inhalation

The aerodynamics of aerosols and their deposition on a facial mask play a critical role in determining the effectiveness of respiratory protection. Existing studies have emphasized the risks of aerosol dispersion caused by exhalation, vocalization, and coughing. In contrast, little attention has been given to aerosol aerodynamics in an open environment, which allows aerosol to circumvent the mask, during inhalation. In this study, we experimentally examined aerosol flow around a facial mask and subsequent aerosol deposition with varying inhalation pressures. Our results indicate that aerosol flow in the vicinity of mask surface behaves like a viscous flow as stagnation within the range of human breath flow. In this range, it is found that the the amount of deposited aerosols can be formulated by modifying the previous aerodynamics theory. As the inhalation pressure increases and exceeds the human breath flow rate, the amount of deposited aerosols is observed to deviate from the theory, which is caused by inertial effect. Additionally, it is observed that denser masks provide a delayed arrival of aerosols on the mask surface, which can help reduce the risk of infection.