Did you know homemade face masks made of cotton are about 20 percent more effective at filtering out small particles like SARS-CoV-2, the virus that causes COVID-19, than silk or flannel? And have you heard that after two weeks of wearing any of these three fabrics over your nose and mouth, you could potentially prevent up to 19 or 20 people from contracting the virus?
Two friends in Poland are on a mission to make sure you're aware of these facts—and to dispel misinformation surrounding protective face coverings. And the best way to do that is with a calculator.
Dominik Czernia, a physics Ph.D. student at the Institute of Nuclear Physics in Kraków, and Joanna Michałowska, a Ph.D. student at the Poznan University of Medical Sciences, have created their free calculator—hosted on Omni Calculator, a repository of over 1,290 calculators across various kinds of subject matter—to illustrate a few variables around mask-wearing and their consequences.
"There are lots of people that don’t believe in mask efficiency," Michalowska tells Popular Mechanics. "There are also lots of Facebook posts saying that you can get a fungal infection, or some other disease [from wearing a mask], and none of these things have been proven."
To build the calculator, the pair parsed through data from a few new coronavirus-related research studies. One study, published in the journal ACS Nano in April, shows the effectiveness of a number of different materials used in homemade cloth masks, from cotton, to silk, and even chiffon. Those researchers found when it comes to homemade masks, hybrid materials are best—think cotton-silk or cotton-flannel blends.
The Best Face Masks for Your Buck
In Czernia and Michalowska's calculator, this is accounted for in the drop-down menu for mask type. There are options for N-95 respirators, surgical masks, and scarves, too, if you want to check out how well those coverings filter out small particles.
From there, the other variables include:
📍 Whether or not you wear a mask: This is a yes or no option, and if you toggle to "no," the calculator states that, all other variables held constant, your actions could cost up to one life and lead to 20 new infections.
📍 Initial reproduction number R₀: Pronounced "R-naught," this is a mathematical term that describes how contagious an infectious disease is. Czernia and Michalowska set the R₀ to a default of 2.5, since COVID-19 has an R₀ of roughtly 2.4 to 4.0, with 2.5 being the best current estimate, according to the U.S. Centers for Disease Control and Prevention.
Basically, this means each person spreads the disease to two to four others, on average, if no other measures are introduced (like quarantining, or wearing a mask). For the most realistic results, leave this variable alone when you try out the calculator.
📍 Percentage of people that wear masks: This is set at a default of 100 percent, but considering many people incorrectly wear masks beneath their nose, or don't ensure a proper seal, you may want to lower that number. Plus, there's a vocal minority of people in the U.S. who refuse to wear a mask in public. According to a June 2020 poll from Pew Research Center, about 65 percent of respondents said they always or mostly wear masks inside businesses.
Let's run through a test scenario. I used my personal preferences, but feel free to play around with the calculator on your own by clicking here. I selected "Yes" for wearing a mask and set the material to cotton, since that's what most of my homemade face coverings are made with. I kept the R₀ at 2.5, but moved the percentage of other people who wear a mask down to 65 percent, since realistically, not everyone will put one on.
My results show that my individual actions could potentially protect up to 19 others from an infection, possibly saving one life if you take the COVID-19 mortality rate into consideration.
It took Czernia and Michalowska three days to build and test out the calculator. Based on the traffic that other Omni Calculators see, the students expect at least 10,000 to 20,000 people will use theirs each day. It's one small way they hope to stop the spread of COVID-19. Information is everything, they say.
"If someone is choosing to not wear a mask, the calculator will show that people may die because of your actions," Michalowska says. "But wearing a mask actually stops the epidemic."
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