• Visualizing droplet dispersal for face shields and masks with exhalation valves
• 

FIG. 1. (a) A face shield, which is similar in design to those used by healthcare workers in conjunction with masks and other protective equipment. The vertical laser sheet used for visualizing the expelled droplets is visible in this panel. (b) An N95 mask with an exhalation valve located at the front. Both cloth-based and N95 masks can be found equipped with such exhalation ports.

FIG. 2. Near-field view of the droplet spread when a face shield is used to impede the emerging jet. (a) Prior to emulating a cough/sneeze, (b) 0.57 s after the initiation of the emulated cough, (c) after 3.83 s, and (d) after 16.57 s. The ejected plume is illuminated by both a vertical and a horizontal laser sheet. Droplets illuminated by the horizontal laser sheet can be observed in (c) and (d). Multimedia view: https://doi.org/10.1063/5.0022968.1

FIG. 3. Far-field view of droplet spread when a face shield is used to impede the jet. (a) 2.97 s after the initiation of the emulated cough, (b) after 6.98 s, and (c) 10.77 s. Multimedia view: https://doi.org/10.1063/5.0022968.2

FIG. 4. Visualization of the droplet spread when an N95 mask equipped with an exhalation port is used to impede the emerging jet. (a) Prior to emulating a cough/sneeze, (b) 0.2 s after the initiation of the emulated cough, (c) after 0.63 s, and (d) after 1.67 s. Multimedia view: https://doi.org/10.1063/5.0022968.3

FIG. 5. Visualization of droplet spread when a regular N95-rated mask is used to impede the jet. (a) Prior to emulating a cough/sneeze, (b) 0.13 s after the initiation of the emulated cough, (c) after 0.33 s, and (d) after 0.83 s. Multimedia view: https://doi.org/10.1063/5.0022968.4

FIG. 6. Visualization of the droplet spread when a surgical mask (brand “A”) is used to block the jet. (a) Prior to emulating a cough/sneeze, (b) 0.37 s after the initiation of the emulated cough, (c) after 0.62 s, and (d) after 2.33 s. Multimedia view: https://doi.org/10.1063/5.0022968.5

FIG. 7. Visualization of droplet spread when a surgical mask (brand “B”) is used to block the jet. (a) Prior to emulating a cough/sneeze, (b) 0.5 s after the initiation of the emulated cough, (c) after 0.83 s, and (d) after 3.13 s. Multimedia view: https://doi.org/10.1063/5.0022968.6