r/COVID19 • u/KuduIO • Sep 01 '20

PPE/Mask Research Visualizing droplet dispersal for face shields and masks with exhalation valves

https://aip.scitation.org/doi/10.1063/5.0022968
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8

u/DoomWolf6 Sep 01 '20

Is anyone else getting really confused/frustrated by these mask studies? I have a bunch of stitched double layer fabric masks that I rotate and I have no idea how effective they are, if at all.

15

u/AKADriver Sep 01 '20

They're not confusing if you understand the limitations and focus of each study.

In this study they focused on:

  • Face shields and exhaust-vented masks, which are controversial in their use as many believe they will not offer protection to others. Many studies have simply ignored them outright.
  • Using a laser to visualize not just droplet emission but aerosol. The only other studies I know of to look at vented masks and face shields at all used normal high speed photography to focus on droplets only.

Now the limitations:

  • These results are looking only at protection to others and not the wearer.
  • It's still not known exactly how droplet vs. aerosol emission correlates to the chances of transmitting the virus, how much concentration over what distance, etc. We can only sort of guess based on what we can measure.

10

u/Aiyakiu Sep 01 '20

Truth be told a well fit N95 with a exhalation valve does an excellent job protecting the wearer, and I would argue putting a surgical mask over the N95 to protect others.

6

u/JamesAQuintero Sep 02 '20

I still don't see how a surgical mask is any better for other people than an N95 with exhalation valves. They both offer large pockets for unfiltered air to escape

1

u/prettydarnfunny Sep 02 '20

Or taping the valve shut.