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This post comes courtesy of Smart Air (smartairfilters.com), a social enterprise and registered B-Corp dedicated to helping people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.
Scientists from the University of Cambridge asked this exact question in the aftermath of the 2009 H1N1 flu pandemic. They thought that in a global pandemic scenario, we might run out of N95 masks. Their predictions have come true during the coronavirus outbreak.
The homemade cotton masks captured 71 percent of 0.65-1.1 micron particles, compared with 86 percent for the surgical mask. Although the surgical masks captured 15 percent more particles, the cotton masks did surprisingly well. The researchers concluded that homemade masks would be better than nothing.
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The Cambridge data shows that homemade masks can filter out some particles that are 0.65-1.1 microns in size. That’s pretty good, however, most viruses are smaller than this, and the coronavirus is 0.1 microns. A group of researchers in the Netherlands tested homemade masks made from a tea cloth for smaller particles, that are more similar in size to viruses.
They tested what percentage of particles the masks could capture for even smaller particles than the Cambridge researchers: from 0.02 to 1 micron. They used a fit-test machine to test the masks while people were actually wearing them.
They then tested the masks’ effectiveness after people had worn them for three hours. The results showed that moisture and time had very little impact on effectiveness for any of the masks.
In fact, the homemade masks actually got 5.8 percent more effective at filtering virus-sized particles after three hours. From this, we can conclude that wearing homemade masks for several hours won’t reduce their effectiveness.
Next, they tested homemade masks with 11 children aged five to 11 years old. When kids wore the homemade masks, they removed just 52 percent of the 0.02-1 micron particles. That’s almost 15 percent less effective on kids than on adults.
Data shows that homemade masks made with a single layer of cotton clothing or a tea towel can remove around 50-60 percent of virus-sized particles. This means they perform worse than surgical masks and FFP2 (N95) masks. Wearing the homemade masks for three hours had no significant effect on the filtration efficiency.
This post originally appeared on the Smart Air WeChat official account.
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