Testing Efficacies of Facial Masks in Mitigating Transmission of Aerosolized Droplets Emitted During a Cough*

1. In response to and in the wake of the COVID-19 pandemic, the importance of face masks has been realized. In evaluating the effectiveness of various types of face masks, regulators aim to quantify the outward leakage of aerosolized droplets from the masks using manikin head forms and emulated coughs. We examine the laboratory techniques used in such evaluations through flow visualization and particle count measurements of the outward leakage associated with various masks using a head form with soft skin compared with that using a hard plastic head form, in support of characterizing such head forms used for testing efficacies of masks.  A set of eight masks were tested using an advanced static head form with soft skin and a corresponding 3-D printed plastic hard-skin head form. Measurements from two particle counter sensors, aided by Flow visualization in a laser light sheet, were used to characterize the spread of aerosolized droplets from a simulated cough and the concentration of the resulting outward leakage from each mask. Results of the tests performed will be discussed. They show that the majority of the leakage is observed to be around the nose bridges of the head forms and that the outward leakage from a mask donned on a soft skin head form is generally lower than if it was donned on a hard skin head form. Results of a comparison between N95 and other masks will be presented.