Can DIY Masks Capture Viruses?
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 researchers asked volunteers to make their own masks using cotton t-shirts and a sewing machine, using a simple protocol they’d devised. Then the researchers shot tiny 1-micron size bacteria (called “Bacillus atrophaeus”) at the masks and measured what percentage the homemade masks could capture. These particles are roughly the size of the particles behind the plague and anthrax.
The DIY masks captured fewer particles than the surgical mask, but they still managed to capture 69% of 1-micron particles.
But is that the smallest particle homemade masks can capture? The researchers stepped it up a notch by shooting .02-micron “Bacteriophage MS2” particles at the masks. These are even smaller than coronavirus particles.
Again, the surgical mask captured more particles, but the homemade cloth mask captured 51% of these nanoparticles.
OK, But They’re Leaky, Right?
At this point, smart skeptical readers are probably thinking, “sure, cloth can capture particles, but they probably don’t seal around the face, so they’re ineffective.”
Fortunately the researchers fit-tested the DIY masks too. In fit-tests, scientists measure the number of particles inside the mask versus outside the mask while someone is actually wearing the mask.
The fit-test machine measures particles from .02 to 1 microns, which includes the
size of the coronavirus.
Across 21 volunteers, the homemade cotton masks captured 50% of 0.02-1 micron particles, compared with 80% for the surgical mask. Thus, DIY masks still managed to capture particles while people were actually wearing them. Based on this data, the researchers concluded that homemade masks would be better than nothing.
