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For homemade face masks, 3 layers are better than 1

09 August 2020

Health Desk :

Masks can prevent the spread of COVID-19, says the Centers for Disease Control and Prevention (CDC).
According to a new observational study, face masks with up to three layers of material are much more effective than thinner ones.
Another study found silk performs similarly to surgical masks when used together with N95 respirators.
The COVID-19 pandemic has caused shortages of personal protective equipment (PPE), and agencies, like the Centers for Disease Control and Prevention (CDC), have recommendedTrusted Source we use homemade cloth face masks as an alternative.
Masks can prevent the spread of COVID-19, and the CDC provides instructionsTrusted Source to make your own. The CDC advises that even a bandanna face covering is sufficient to reduce virus risk.
However, recent research finds that just covering your nose and mouth may not be enough.
According to a new observational study, published in the journal Thorax, face masks with up to three layers of material are much more effective than thinner ones.
Single layer not good enough for all situations
Australian researchers used LED lighting and a high-speed camera to record how a healthy individual wearing different masks scattered droplets in the air by sneezing, coughing, and speaking.
Using the specially designed lighting system and high-speed video, they recorded how a healthy person dispersed airborne droplets during speaking, coughing, and sneezing while wearing different types of face masks:
single-layer T-shirt material
sewn, two-layer
three-ply Bao Thach activated carbon face mask
The single-layer face mask was made from a folded piece of cotton T-shirt and hair ties following the CDC recommended no-sew methodTrusted Source, and a two-layer mask was produced following the CDC guidelinesTrusted Source for a sewn mask.
"Single-layer cloth mask is not as effective as a standard paper surgical mask. If you're going to use a cloth mask, you should use one that has at least two or preferably three layers," William Haseltine, PhD, chair of the US-China Health Summit, founder of Harvard University's cancer and HIV/AIDS research departments, and author of "A Family Guide to COVID," told Healthline.
Video confirmed that a three-ply surgical face mask was most effective at reducing airborne droplet dispersal from sneezing and coughing. A single-layer face covering only reduced droplet spread from speaking.
"A surgical mask was the best among all the tested scenarios in preventing droplet spread from any respiratory emission," concluded the study authors.
Common fabric has advantage over cotton
Meanwhile, University of Cincinnati (UC) biologists investigated commonly available fabrics to find which can best protect against virus spread, to address personal protective equipment shortages.
"We're trying to address this critical problem. Healthcare workers still don't have enough personal protective equipment, namely N95 respirators or basic surgical masks," said Patrick Guerra, PhD, assistant professor of biology in UC's College of Arts and Sciences in a statement. "Cotton traps moisture like a sponge. But silk is breathable. It's thinner than cotton and dries really fast."
The study, published ahead of peer review, concluded that silk performs similarly to surgical masks when used in together with N95 respirators. It also has the advantages of being washable and water repellent, which researchers say helps to keep individuals safer from the COVID-19 virus. They observed that silk worked much better as a moisture barrier than polyester or cotton, two materials that quickly absorb water droplets.
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Silk effectively repels droplets
"As a protective barrier and face covering, silk is more effective at impeding the penetration and absorption of droplets due to its greater hydrophobicity [water-repelling ability] relative to other tested fabrics," study authors wrote. Although this research focused on silk to extend the life of N95 masks, the findings indicate silk may be a good idea for improvised, multilayer masks as well.
Haseltine emphasized that preventing droplet spread is key to reducing COVID-19 transmission, and people shouldn't worry too much about the material used in a mask.
"As long as your mask prevents droplets from exiting your nose and mouth, such as a paper surgical mask does, it will help prevent the transmission of COVID," said Haseltine.
Manufactured masks still best choice
Manufactured surgical masks are better made than ones we improvise, and studiesTrusted Source find N95 respirators are more effective against finer aerosols and likely better at preventing droplet transmission.
However, researchTrusted Source finds that while the homemade masks may be less effective than surgical masks, they're still better than not wearing one at all.
"When using a mask, it is important to pay attention to the variable nature of the cloth," said Haseltine. "Some cloths are tightly woven, some cloths are loosely woven. The more tightly woven the material, like the material of a manufactured surgical mask, the better protected one is against COVID aerosols and droplets."
 "I think if we could get everybody to wear a mask right now I think in 4, 6, 8 weeks we could bring this epidemic under control," CDC Director Dr. Robert R. RedfieldTrusted Source, said in a recent interview.
He also emphasized that now is the time to wear face coverings, and the data is clear that "masking works, whether it's a simple surgical mask or something used in a clinical setting."
The bottom line
The pandemic has caused shortages of personal protective equipment, so many of us are relying on improvised face coverings.
New research finds although the CDC recommends even a single-layer cloth mask as protection, two or three layers are best.
Experts say that even a single-layer mask is better than no mask at all, and if we embrace masking now, the pandemic might be controlled within weeks.

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