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CLEVELAND, Ohio – You can buy all kinds of masks, but which ones are the best for preventing droplets containing coronavirus from getting through? Scientific studies show that multiple layers of tissue and multiple nose threads can help prevent the spread.
Masks are at the center of Ohio’s latest coronavirus strategy, with Governor Mike DeWine announcing on Wednesday night increased enforcement of the state’s mask mandate. Common types of masks include sheet masks and disposable surgical masks.
Cleveland.com reviewed 12 studies on the effectiveness of masks, based on research published in leading scientific journals. When deciding to buy or make a mask, recent research cites three key factors: fabric, fit, and ties.
The gold standard for healthcare professionals is always a properly adjusted N95. However, experts told cleveland.com that N95s are impractical for everyone to wear. There are many consumer choices that can make masks work better. N95s are commonly used in hospitals and need to be properly fitted, which is why the general public normally uses surgical or cloth masks.
Keep in mind that wearing even a simple mask can help stem the spread of disease, although a mask is not a substitute for proper social distancing and hygiene measures.
In shape
Fit is a theme throughout the published literature on the effectiveness of masks, although research experiments with fabric are more than adequate.
A study published in Nature on the effectiveness of masks and face coverings notes the potential importance of fit in the context of the study results. Surgical masks and unventilated N95s reduced emission rates by 90% and 74%, respectively, regardless of the fit. The researchers noted that the N95s in this study did not perform as well as a surgical mask.
“The imperfect fit of the KN95 respirators may allow greater evacuation of particles from the mask-covered environment compared to more flexible surgical masks,” the authors wrote. “Regardless, all of the surgical masks, KN95 and N95 respirators tested here resulted in a substantial reduction in particulate emissions compared to no mask.”
Simply wearing the mask is therefore useful, although there are enough ways that people wear it incorrectly that internet memes will laugh at them. Covering the nose with a mask is crucial, so leaving it hanging over the chin or tight under the nose will not work.
The way a normal fabric mask is structured can leave gaps between the cheek and the mask, which could lead to virus leakage issues. Essentially, the jet of air that comes out of the mouth while breathing or speaking will seek a path where it is not blocked. If there is a space where the material does not cover it, the air will be redirected through these holes instead of being filtered through the mask.
A study published in “Physics of Fluids” tested the effectiveness of cloth and commercial masks in obstructing the flow of air containing respiratory droplets, which researchers recognize as a primary method of transmission of the coronavirus. In a demonstration for “Good Morning America,” the researchers showed the difference in their modeling in a common blue surgical mask. When the researchers did not press down on the wire nose clip for the mask, there was more leak out of the top of the mask.
“The main thing to keep in mind is to make sure that it fits the face perfectly and with any wire or metal band present, you should always try to press it down so that it hugs your face well. “Dr Sid Verma told GMA. .
A study published in Extreme Mechanics Letters showed that surgical masks or fabric masks that are not fitted could allow significant leaks. Trying to find a cloth mask with a thread that fits your nose and face can help narrow the gaps. Researchers at the University of Illinois also suggested in the Extreme Mechanics Letters study that a more breathable fabric may help distribute airflow, reducing leakage through unfiltered areas. Adding another layer of fabric to the mask also looks promising, although published research on this is limited.
Connections
The most common type of mask relies on earrings rather than ties. Apart from some users complaining of discomfort around the ears, some studies show that attachments that go behind the head can be safer and work better.
The researchers looked at 29 types of respirators and face masks and found that in all tests, masks with tethers outperformed those with earrings. For example, in tests for surgical masks, the filtration efficiency – how well the mask gets stuck – was found to be almost double that of masks with tether like those with earrings.
Because the researchers tested the effectiveness while the subjects moved, they concluded that the earrings might not provide enough tension to keep the mask snug.
Adjustable earrings could help with the fit. A best practice review for fabric masks found that users should hold their mask against their nose and mouth while fastening neckties or earrings. When you tie a mask with ties behind the head, tie the top tie around the back of the head, then at the base of the neck.
Fabric
There are many considerations when choosing a fabric for a mask. Take a look at a regular surgical mask. Behind the pleated front, the layers of fabric can come apart. Several layers play different roles in preventing the coronavirus from spreading. One layer could soak up large droplets, preventing them from spreading the coronavirus (but causing you to throw off or wash off a mask.) Then another would filter the smaller aerosol particles.
Having several layers of different fabrics can also help with humidity. Fabrics are grouped into hydrophilic and hydrophobic, which means that the fabric either retains moisture or repels moisture. Having these two types of fabric in a mask design can be helpful in blocking droplets.
The number of layers is important when selecting a mask. Researchers at Cambridge University and Northwestern University tested a wide range of fabrics that can be used in homemade masks. Multi-layered fabrics performed better than full-surface single-layered fabrics. Cotton and heavy cotton did a good job of filtering out fine particles. Other fabrics, like windbreaker and denim, have shown a higher filtration rate, but are not as breathable.
“A mask that blocks particles very well but restricts your breathing is not an effective mask,” author Eugenia O’Kelly of the Cambridge Engineering Department said in an article on the university’s website.
“Denim, for example, was pretty good at blocking out particles, but it’s hard to breathe, so it’s probably not a good idea to make a mask out of an old pair of jeans. N95 masks are much easier to breathe than any fabric combination with similar filtration levels. “
A review of 25 articles referring to sheet masks, published by the Mayo Clinic, found that fabrics with a higher thread count performed better than those with lower masks, and even better when layered. Researchers recommend cotton with a thread count of at least 100 threads per inch. Pleated masks are also recommended, which allow the user to easily pull the mask up to the chin.
The “Physics of Fluids” study showed that wearing a bandana-style mask is significantly less effective than other masking methods. If you choose to wear a gaiter, make sure there are multiple layers in the gaiter, the Centers for Disease Control and Prevention recommends.
Silk could also be a promising fabric for masks, according to a study published in Plos One. One of the authors, a professor at the University of Cincinnati, studied the effectiveness of silk after considering the water resistance of cocoons of silk caterpillars, he told Discover Magazine. Silk has surpassed polypropylene, used in disposable surgical masks, and cotton, in repelling water. Silk is also breathable.
So how do you choose a mask?
The most important aspect of masking is wearing one and wearing it correctly, as well as following social distancing guidelines and avoiding crowds.
When choosing a mask or creating your own, first check if there are at least two layers. Next, assess the fit on your face and if there are any gaps that could be corrected with a nasal thread along the top of the mask or folds. These basics can help you choose the right mask for you. When in doubt, a surgical mask with a thread for ease of fit addresses many of these considerations, although the price can add up and experts are concerned about the impact on the environment.
Also, be sure to wash reusable masks frequently, especially after being in areas at higher risk for coronavirus.
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