Second to N95 masks are the standard surgical masks made from non-woven polypropylene. The study showed that hand-made masks had some effect, provided they were made from cotton materials. The cotton was effective in reducing the level of spray generated through everyday speech. However, other self-made face coverings, like bandanas, neck fleeces and balaclavas were very ineffective.
The study, which was developed to provide useful data during the coronavirus pandemic, comes from the Duke University Medical Center and it set out to assess the relative effectivity of different face coverings. The findings are not good news for the wave of ‘fashion-centric’ masks that are appearing, many of which are being touted by so-called social media influencers. This includes Kim Kardashian West, who launched a range of face coverings that sold out within an hour of release.
According to one of the researchers: “The notion that ‘anything is better than nothing’ didn’t hold true.”
To reach their conclusions, the research group worked with Dr. Martin Fischer, who is the director of the Advanced Light Imaging and Spectroscopy facility at the university. The physicist designed a simple test method for mask and face covering effectiveness, based on a box, a laser, a lens, and a cell phone camera. The device detects the scattering of water particles, which are generated as a person speaks.
Details about the methodology are outlined in the following video:
In terms of relative, mean droplet efficiency, the N95 mask had a droplet count below 0.001; a surgical mask around 0.01; a self-made cotton mask of around 0.1; and many other materials close to 1.0 (which was almost identical to wearing no face covering at all).
While some masks are better than others, and many face coverings should be avoided, the researchers note that masks are a good idea, especially given that around half of COVID-19 infections come from people who do nor show symptoms, and often do not know they’re infected.
Based on the research findings, the scientists recommend that authorities should be providing free masks, of an appropriate quality, as a minimum to at-risk individuals and areas of high poverty where ow income prohibits people from purchasing masks.
The research appears is in the journal Science Advances, with the research paper titled “Low-cost measurement of facemask efficacy for filtering expelled droplets during speech.”
