If you are not sure if a face mask is worth wearing, or if you need to wear a mask but you are not sure what type, our new research should help you decide.
We shoot videos of what happens when you talk, cough, and sneeze in different settings, without wearing a mask, two different types of cloth masks, or a surgical mask.
The results, published in the magazine. Chest, are clear.
A surgical mask was most effective in blocking drops and sprays from speaking, coughing, and sneezing. But if you can’t get one, a cloth mask is the best option, and the more layers the better.
This is what we did and what we found
You can become infected with the coronavirus, but show no symptoms. Therefore, you cannot identify an infected person just by looking at them. And you may be infected (and infectious) but not know it.
Therefore, we wanted to compare how effective different types of masks were in preventing external transmission of drops while talking, coughing, and sneezing. These are the types of masks that the public could use to reduce community transmission.
We compared the use of no mask with two different types of cloth masks made from DIY templates provided online (one mask had a single layer of cloth; the other had two layers) and a three layer surgical mask.
To visualize drops and sprays that you would not otherwise see, we used an LED lighting system with a high-speed camera.
We confirm that even talking generates substantial drops. Coughing and sneezing (in that order) generates even more.
A three-layer surgical mask was significantly better than a single-layer cloth mask in reducing droplet emissions caused by talking, coughing, and sneezing, followed by a double-layer cloth cover.
A single-layer fabric cover also reduced the spread of droplets caused by talking, coughing, and sneezing, but it was not as good as a two-layer fabric mask or surgical mask.
We don’t know how this translates into infection risk, which will depend on how many asymptomatic or mildly symptomatic infected people are present. However, it shows that a single layer is not as good a barrier as a double layer.
What does this mean?
With the mandatory use of masks in Greater Melbourne and Mitchell Shire, we can face a shortage of surgical masks. Therefore, it is important to understand the design principles of cloth masks.
We don’t test more than two layers, but in general, more layers are better. For example, a 12-layer fabric mask is as protective as a surgical mask and reduces the risk of infection by 67 percent.
We recognize that it is difficult to sew 12 layers of fabric. But there are steps you can take to make fabric masks more effective. You can:
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increase the number of layers (at least three layers)
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use a waterproof fabric for the outer layer
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choose a fabric with a high number of threads (so a tighter weave, for example of a good quality sheet, is generally better than a fabric with a looser weave where you can clearly see the light)
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Hybrid fabrics like cotton-silk, cotton-gauze or cotton-flannel can be good options because they provide better filtration and are more comfortable to wear
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make sure your mask fits and seals well around your face
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Wash your mask daily after using it.
The evidence is increasing
In practice, we don’t yet know which one has a bigger effect: wearing masks to prevent infected people from spreading to others or protecting people who inhale infected sprays. Both are probably equally important.
In Missouri, two infected hairdressers continued to work while infectious, but wore a mixture of cloth and surgical masks, as did their 139 clients. No client was infected.
However, a hairdresser infected family members in her home, as she did not wear a mask in her home, and neither did her family.
This is reassuring evidence that the risk of infection is reduced when everyone wears masks.
How to make your own cloth mask
During widespread community transmission, a mask or homemade face covering can make a difference, both by protecting people well and by blocking infected sprays and drops from an infectious person.
So, as many Victorians start living in mandatory face masks, research from our group and others suggest that throwing a scarf over your face is not as protective as a well-designed fabric mask with multiple layers.
The Victorian government provides instructions on how to make a good cloth mask. There are plenty of videos showing how, including a seamless method. There are also community groups that make cloth masks and provide useful information.
C Raina MacIntyre, Professor of Global Biosecurity, NHMRC Principal Investigator, Head of Biosecurity Program, Kirby Institute, UNSW; Abrar Ahmad Chughtai, Epidemiologist, UNSW; Charitha de Silva, professor, UNSW; With Doolan, Professor, School of Mechanical and Manufacturing Engineering, UNSW; Prateek Bahl, PhD Candidate, School of Mechanical and Manufacturing Engineering, UNSW, and Shovon Bhattacharjee, PhD Candidate, The Kirby Institute, UNSW.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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