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There is a simple trick to check if our mask provides reasonable protection against coronavirus infection. You have to put it on and try to blow out the candle. If we can’t put out the flame, test passed. American scientists tested the most popular masks in a more professional way. Here are the results of their work.
- The World Health Organization recommends making masks from three layers of fabric (absorbing, filtering and impervious)
- N95 and surgical masks fared best in tests
- One-way valve masks can spread the infection
- The ranking of the masks was based on tests carried out in various conditions, so it is difficult to treat it as a scientific study
- You can find more such stories on the TvoiLokony home page
We remind you of the text that appeared in Medonet in September 2020.
An ideal mask should block both large airway droplets when coughing or sneezing (the primary method of infecting others) and smaller airborne particles. The latter are aerosols, formed when people talk or breathe out.
We know for sure that the mask must fit tightly to the nose and mouth, as any gaps or vents allow droplets containing potential viruses to enter.
Assuming that the masks are worn correctly, we can take a look at the materials they are made of. Some fabrics filter better than others. The latest American research helped to compile the following list:
Ranking of the effectiveness of the masks in order from best to worst
1. N95. Large droplet filtering efficiency – 99,9%, aerosol – 95%.
2. Surgical mask. Large droplet filtering efficiency – 98,5%, aerosol – 89,5%.
3. Hybrid mask. Large droplet filtering efficiency – 96%, aerosol – 94%.
4. Double-layer cotton mask. Large droplet filtering efficiency – 99,5%, aerosol – 82%.
5. The mask is made of a cloth for wiping dishes. Large droplet filtering efficiency – 98%, aerosol – 72,5%.
6. 100% knitted cotton mask. Large droplet filtering efficiency – 97%, aerosol – 51%.
7. Natural silk mask. Large droplet filtering efficiency – 56%, aerosol – 54%.
8. Scarf, shawl or bandana. Large droplet filtering efficiency – 44%, aerosol – 49%. This protection is a last resort.
9. Mask with valve or vent. Large droplet filtering efficiency – 90%, aerosol – 90%. These masks do not protect those around us.
Order Vitammy professional disposable surgical masks you can buy today at Medonet Market. See the remaining offer of masks available on the website.
«Hybrid» masks offer good protection and you can sew them yourself
Generally speaking, the tighter the weave of the mask fabric, the more effectively we are protected. Therefore, fabrics made with more threads per square inch filter particles better.
It is also recommended to sew masks from several layers of fabric. In the case of fabric masks, the World Health Organization proposes three layers: the inner layer, which is responsible for absorption, the middle filtering layer, and the outer layer, made of non-absorbent material.
You can order reusable, good-quality protective masks that filter particles at the level of over 97% at medonetmarket.pl.
- Seven myths about masks that you need to forget as soon as possible
N95 maskswhose name refers to their 95%. efficiency in filtering aerosols, giving the best protection. They fit snugly around the nose and mouth, letting very few virus particles pass. They also contain special fibers that filter pathogens from the air.
A study by Duke found that the N95 mask allowed less than 0,1 percent transmission while speaking. droplets. That is why this type of masks is most often used by health care workers.
Disposable surgical masks they are also made of a special non-woven fabric. A 2013 study found that they were three times more effective than homemade face masks at blocking aerosol containing flu viruses. At least when the airflow is slower than when you cough, but faster than when you breathe with light exertion.
However, a mask that will be as effective as the N95 or a surgical mask, the so-called hybrid, we can sew it ourselves.
This is evidenced by a study conducted in April at the University of Chicago. It was shown that «hybrid» masks – consisting of two layers of cotton with a weave density of 600 threads per square inch combined with another material such as silk, chiffon or flannel – filtering at least 94%. small particles (less than 300 nanometers) and at least 96 percent. large (above 300 nanometers). Two layers of cotton with a density of 600 threads per square inch provide a similar level of protection against large particles, but are not as effective at filtering out aerosols.
These measurements were taken at low airflow rates, so protection against infection by coughing or sneezing may be reduced. A mask made of several layers of high-density cotton will also work much better than a similar one made of a dish cloth or a cotton T-shirt.
Silk and cotton have different properties
A study published in the Journal of Hospital Infection in June confirmed that masks sewn from vacuum cleaner bags were the most effective alternative to surgical ones. The next places were taken by those made of cloths, pillowcases, silk and cotton T-shirts.
In contrast, tests at the University of Illinois showed that a mask made from a new dish cloth is slightly more effective than a mask made from a used cotton T-shirt. Scientists focused on filtering the droplets formed when coughing, sneezing and talking. The discussed analysis (which is still awaiting a review) also indicates that the used blouse with 100 percent. silk filters the droplets more efficiently with the rapid flow of air. This is probably because silk has electrostatic properties which help it trap smaller particles.
- Six ways to protect yourself from coronavirus infection that are not worthwhile. Scientists debunk myths
Meanwhile, the results of research conducted at the University of Chicago contradict the thesis about its excellent parameters. Researchers there found that a single layer of natural silk filtered out only 54 percent of it. small particles and 56 percent. large. In turn, four layers of this material filtered out 86 percent. small particles and 88 percent. large with little air flow.
Bandanas are ineffective and valve masks are dangerous
In most studies, bandanas and scarves performed poorly. Tests published in the Journal of Hospital Infection showed that the scarf reduces the risk of infection by 44 percent. in the case of staying in the same room with an infected person for no longer than 30 seconds. After 20 minutes, the risk of infection drops by only 24%.
Researchers at Duke University found that bandanas reduced the aerosol penetration rate by half, placing them at the end of the ranking.
Although each mask is better than no mask, there is an exception to this iron rule. The US agency CDC warns against using masks with built-in valves or vents. One-way valve masks can throw infectious particles into the atmosphere, helping the spread of infection.
Disadvantages of the mask ranking
Of course, masks work differently depending on how they are worn. However, during tests, it is not always possible to simulate their operation in natural conditions. This is because it is difficult to recreate the size of the coronavirus particles. Therefore, most studies have evaluated the effectiveness of face masks based on influenza viruses.
- Can you wear a face shield instead of a mask? Experts: The answer is no
In addition, it is still uncertain to what extent the virus is spread via aerosols, as it is extremely difficult to isolate and study the pathogens contained in them. Some scientists define the aerosol itself differently. The generally accepted classification says that the size of the particles in the suspension must not exceed 5 microns (which is roughly the size of the dust particle), however, many experts believe that the determination is completely arbitrary.
Finally, research tests masks under different circumstances: some with intense airflow, such as when coughing, and others with a slower flow of air, such as speaking or breathing, which substantially affects the results.
See also:
- Can disposable masks be reused? [WE EXPLAIN]
- How to wear, remove and clean masks? Avoid these mistakes
- Experts warn: masks are less effective in rain. Why? [WE EXPLAIN]
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