The body of evidence continues to grow: masks protect the person wearing them against COVID-19, in addition to those around them. But with so many choices, what is your best option?
© Karl Gelles / USA TODAY
masks effectiveness
Despite mask type, fewer particles of coronavirus pass through to people wearing face masks, according to a new paper that will be published shortly in the Journal of General Internal Medicine. Fewer particles can result in milder infections if the virus spreads through it.
Another study, published last month, compared the COVID-19 growth rate before and after mask mandates in 15 states and the District of Columbia. It found that mask mandates coincided with reductions in daily COVID-19 growth rates.
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Testing the effectiveness of coronavirus masks
While working on another recently published study, Duke University researchers evaluated the effectiveness of 14 different types of masks by estimating how many drops traveled through the mask during normal speech.
The researchers used a laser beam, a lens that rotated a laser beam in a light sheet, and a mirror that reflected light in a dark box made of cardboard. People spoke the same saying in the coffin with, and without a mask. The particles that hit the lens produced visible fluids captured by the camera of a phone at the other end of the box.
“The most important point of this paper is that we propose a very simple, easily duplicated system in which community groups can actually test masks themselves,” said one of the study’s co-authors, Warren S. Warren, a professor physics, chemistry and radiology at Duke.
So what is the most effective type of mask against COVID-19?
The solid dots represent results of 10 threads for a mask through one speaker. The hollow circles represent the relative drop counts for four speakers.
Fitted mask of N95
Medical N95 mask without exhalation valve proved to be most effective. However, the CDC does not require the general public to wear N95 respirators, which are restricted in supply so that they can be reserved for health care workers and first responders.
2. Three-layer surgical mask
When study participants said the phrase “stay healthy, people” with a three-layer surgical mask, only a small fraction of drops came through.
Surgical masks are for single use only and are made to protect the wearer’s nose and mouth from contact with drops, splashes and sprays that may contain germs. They also filter out large particles in the air.
3. Mask of cotton-polypropylene-cotton
A mask made of two layers of cotton and one layer of synthetic material proved to be the protective option, except masks intended for medical professionals. Another recent study suggested that a homemade cloth face mask probably needs two or three coats to be effective in preventing the spread of the coronavirus.
A single-layer cover reduced the droplet spread of speech, while the double-layer cover was better at reducing drops of coughing and sneezing, according to the researchers.
4. Polypropylene front mask
This mask had two layers of polypropylene, a soft easily cleaned synthetic fabric. Polypropylene is one of the most popular materials for masks, because viruses and bacteria can not live long on the fabric.
According to a study published in Nano Letters, polypropylene may be one of the best materials for a homemade mask. It has the electrostatic charge that finds incoming and outgoing particles. It loses its electrostatic charge when washed, but can be charged by rubbing it with a plastic glove.
5. Swad
Researchers used a slightly damp washcloth in another experiment. Using video games, they found that saying a simple sentence generated hundreds of drops from 20 to 500 micrometers. The washcloth blocked almost all those drops from the person’s mouth.
6 – 7. Two-layer plush style masks
If you choose the material, make sure the cotton is woven at a high density so that there are no visible pores under light, according to the study in Nano Letters. If this is not the case then maybe this is a good idea to use multiple layers.
“I would not put too much stock in the small differences we saw between the different cotton masks; I would emphasize that fit is important,” Warren said.
8. Valved N95
Researchers noted that although the ventilator does not compromise the wearer’s protection, it can reduce the protection of the people around it, as the masks release exhaled air through their opening, according to the CDC.
The CDC has also recently updated its guidelines advising Americans to avoid face masks with exhalation valves or vents, as they are not as effective in preventing the spread of COVID-19.
9. Olson style masks
The Olson Mask Pattern was named after the nurse who made dust masks to use when medical masks were not available. It is curved to fit the nose and mouth area. These masks are not a substitute for N95 masks in health care environments, but they can be good for personal use.
10. Maximum AT masks
This “1-layer Maxima AT mask” may look a bit like surgical masks, but it does not offer as much protection, according to research.
11. One-layer pleated style mask
The single layer mask performed poorly. The World Health Organization recommends that dust masks have three layers: an inner layer that absorbs, a middle layer, which can be inserted in the middle to act as a filter, and an outer layer made of a non-absorbent material such as polyester.
12. Two-layer wrinkle style mask
It is important to make sure that the mask is properly fitted and covers your nose and mouth. Studies suggest that 60% of users fail to wear surgical masks at first attempt.
When the mask is loose, it allows the possible leakage of air around the sandy areas and can contribute to exposure to aerosols. Having a mustache or beard can also make it challenging to fit the mask well.
13. Knitted stitches
For this, researchers used a mask with a looser tissue.
“Think of the fabric as something more like a sock than comparing it to a bed sheet, which is more than what you have for the standard cotton,” Warren said.
Larger pores in the masks can enter more particles. Washing and drying the mask can further reduce its efficiency.
14. Bandanna
Bandannas proved to be one of the least effective in the study published in June in the journal Physics of Fluids. Although a bandanna can reduce the range of particles expelled during a cough, it scores lower than a non-exposed cough when stopping the smallest aerosolized respiratory droplets.
15. Neck gaiter
A neck gear, an article loved by runners, ranks worse than no mask at all. The porous substance can divide the larger particles into smaller ones. Smaller particles stay in the air longer than large droplets.
However, Warren points out that the study he co-authored was not a large-scale clinical trial, so the results could not be generalized. The outcome for the gaiter was worse because some of the most comfortable masks are normally thin and those do not do a good job of blocking particles.
The gaiter in the study was made from a single layer of polyester-spandex blend. “When we look at the gaiter we used, for example, if you hold the only layer up to a light, stretching what it would be like if it were worn, you can see light through it,” Warren said. “And my feeling is that if that’s the case, it’s not doing a good job of protecting the people.”
This article originally appeared on USA TODAY: Cotton mask as neck gaiter? See how effective different types of masks are
Gallery: Here’s the best and worst face mask, experts say (ETNT Health)
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