Evaluation of the Efficacy and Aerodynamic Intervention of Face Shields against Pathogenic Aerosols Using Computational Fluid Dynamics and Wells-Riley Transport Model

The COVID-19 pandemic has unraveled the historical resistance to the acknowledgment of airborne transmissions. As it is a respiratory disease, the disease is mainly transmitted by coughs and sneezes, which introduce pathogenic aerosols that float while being transported in the air. As the effectiveness of the public health response is just as far as the working understanding of the mechanisms of transmission, physical interventions like wearing face shields – even in public places – were being mandated in the Philippines. With respiratory diseases like COVID-19 being airborne, face shields intervene aerodynamically and not ballistically. Mandating face shields in public spaces has widened the range of scenarios, especially now with the different angles of attack from which the emissions can be coming. The coughs coming from different angles of attack, as well as the performance of face shields in the reduction of transmission, are simulated in an unsteady computational fluid dynamics analysis, with large eddy simulation as the turbulence model. The risk of infection is evaluated based on the transport model of quanta used in the Wells-Riley formulations. Results showed that the face shield is only effective against coughs hitting perpendicular to the surface. At other angles of attack, the protection by the face shield diminishes, and wearing a face shield can instead increase the infection risk against pathogenic aerosols.