In a head-to-head comparison of masks worn by people with active COVID-19, the inexpensive โduckbillโ N95 came out on top, stopping 98% of COVID-19 particles in the breath of infected people from escaping into the air. Led by researchers from the University of Maryland School of Public Health (SPH), results showed other masks also performed well, blocking at least 70% of viral particles from escaping from the source โ an infected personโs exhaled breath.
the methodology is a bit wonky since they switched horses midstream and stopped looking at cloth masks entirely, but the data is worth looking over even so. encouraging to see that surgical masks, while less effective, still block a significant majority of exhaled viral particles.
the most interesting thing to me about this study was the KN95 shocker:
The study found that a common brand of KN95 masks leak more air than duckbills or other studied masks, because they donโt conform to the face well. That flaw is compounded by a powerful filter with more flow resistance that pushes air out of the mask at the sides instead of through the filter, allowing more virus particles to escape into the surrounding air.
the "common brand" was the Powecom KN95, which was especially common at U of M because they were being distributed by the school. really emphasizes that there isn't a one-size-fits-all solution to masking, very literally!! there are just more or less optimal strategies and designs. for me, 3M's Aura N95s fit better than anything else I've tried -- I took a chance on a pack of Walgreens hard shell N95s recently and I can't make them conform to my face at all. thankfully I can tell because of my glasses!1 but I'm positive there's someone else out there for whom the inverse is true.
anyway, covid is still happening, wastewater data in the U.S. is a nightmare, stay cautious!
-
in retrospect the ads I saw in 2020/21 advertising sprays to prevent condensation on glasses are pretty grim
