From a real life fabric expert friend (not merely a FB friend). This is hugely helpful. Please pass it along and stop the bad practices regarding masks.
Q1. Why can't we wear mask made of 100% cotton even if it is difficult to buy surgical masks nowadays?
Although it is easy to DIY cotton mask, but the outcome will be worse than no mask. It seems that we can wash the cotton mask everyday so that the bacteria count is low, but the water flow of DIY mask is two way whilst surgical mask only allows one way flow, means if there is one COVID-19 patient nearby and his/her saliva drops on your face mask, it will spread into the mask as cotton is hydrophilic and will enhance diffusion into the mask. Moreover, due to the humid and warm temperature inside the mask, it will further promote the growth of bacteria. Also as the water flow is two way, the bacteria will reach the face of the wearer if the mask is wet. So it’s not really true that having a mask is better than none, it really depends on the material and construction of the mask.
Q2. Why can surgical mask not be reused, even after sanitization, steaming or washing?
Most ppl may think if surgical mask reached nano type level will filter virus effectively. However, the real concept behind is due to its “electret treatment “ to filter the virus and bacteria, plus the ability to kill bacteria(cannot kill viruses). The electric field built by the electret treatment will create a protective shield to attract the viruses and the ability to kill the bacteria. After 4 hrs or 8 hrs of use, these electric field will consume all its static energy, like a dead smartphone without battery, then the electret treatment will no longer effective to attract viruses. That’s why we can only wear mask for less than one day. This electret treatment is the key concept behind a surgical mask, that’s why even though we can sanitize, steam or wash the mask to reduce the total bacteria count, but we cannot recharge the electric field to make it function again, thus its ability of attracting/filtering the viruses and killing bacteria cannot be revived.
Q3: Does a stuffy mask means better filtration ability?
The answer is, not really, but there are many exceptional cases. We already mentioned in Q2 that surgical mask used electric treatment to handle viruses/ bacteria. The size of COVID-19 virus is 120nm (nanometer), the gap between fibers of surgical mask is over 120 nm, so the virus can penetrate the gap between the fibers and reach our face theoretically. However, the electret treatment will create an electric field to attract those viruses and keep them between the gaps of the fibers, so viruses cannot penetrate through the mask and reach the wearer. The high breathability of mask with electret treatment will let wearer feels more comfortable, whilst still effectively filter viruses(usually larger than 100nm) and bacteria.
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