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N95, KN95, medical and ordinary face mask, which mask can resist the new coronavirus?

Face masks are now a necessity of life, and the prices of N95, KN95, medical masks, and ordinary masks are increasing. But do you know which mask is the most effective, and how big is the difference? Let's analyze it.

Face mask

First of all, let's distinguish between various protective face masks. The most commonly mentioned N95 masks, N means "not oil resistant", 95 means "exposed to a specified number of special test particles, the particle concentration in the mask is lower than the particle concentration outside the mask 95%. Among them, 95% is not an average value, but a minimum value. Of course, there are 95, there are 100, and N100 masks are also available, but because of the very large respiratory resistance, they are rarely used.

KN95 is a national standard, which requires the filtration efficiency of non-oily particles above 0.075 microns in masks to be greater than 95%. In addition, some KN95 / N95 masks are designed with an exhalation valve. During breathing, part of the air is directly discharged through the exhalation valve, which reduces the exhalation resistance, and can prevent the mask from being wet by exhalation to a certain extent, and extend the service life.

Medical masks are divided into medical protective masks and medical surgical masks. Medical protective masks usually meet the N95 standard, and the filtering ability is very strong, while medical surgical masks only provide some basic protection, and the filtering ability is relatively weak, about 70%.

Ordinary masks usually only play a role in heat preservation and moisturization. The filtering ability is very weak, but it can resist some droplets and can also reduce the possibility of infection to a certain extent.

At present, it is basically determined that the new coronavirus can be transmitted by droplets, and all the masks above can actually protect the droplets because the droplets are the droplets flying in the air, and their particle size It is much larger than dust, and the function of the mask is mainly to block rather than filter. Of course, the surface layer of the mask must not use hydrophilic fibers such as cotton fiber, rayon and other materials to prevent the droplets from being blocked by the surface layer and spreading through the hydrophilicity of the fiber.

But there is a problem. The main component of droplets is water. Water evaporates in the form of water molecules. Will the new coronavirus after being evaporated be locked by other residual substances? , But there 
are signs of life, it is uncertain whether the virus will transfer in the fiber. If the virus has the ability to move through the fiber, sooner or later it will move to the inner layer of the mask, and contact with the mouth and nose will cause 
infection.

Therefore, if you use a mask with poor filtering ability, you must replace it frequently. If you communicate with people more frequently, especially in a hospital environment, it is recommended to replace it every 2 hours. It can 
be extended properly at other times. Ordinary masks can be replaced every 4 hours. N95 masks can be changed every 1-2 days.

Protective face mask

When the mask is out of stock, you can put the cleaned mask in a dry place and hang it for 24 h, or dry it at 57 ℃ for 30 minutes, or double the suspending or drying time for safety to 48 h and 60 min, the mask can be used after sterilization. 60 minutes at 7 ℃ will not cause the phenomenon of static electricity degradation, so it can be used repeatedly. However, it is absolutely necessary to avoid the use of solvents or detergents for disinfection or cleaning, because the solvents and detergents will eliminate static electricity. After the static electricity is eliminated, the filtering efficiency of the mask will be reduced from 95% to 50%.