The filtering element of the physical filtering method only needs to consider respiratory resistance. And how long a specification of melt blown material filter cotton can be used, mainly considering static electricity loss and increased resistance. The determination of increased respiratory resistance is relatively simple, but for low environmental dust levels used for antiviral purposes, even if the increase in positive force is not significant, it may be due to prolonged use, excessive air flow, and electrostatic attenuation, leading to a decrease in filtration efficiency.
       Usually high-quality imported filter cotton. The half-life of static electricity is about 250 days, which means that static electricity can decay to half after being left for about 250 days. If it fails before the respiratory resistance increases significantly, the lifespan can be shortened to at least half compared to brand new filter cotton. However, the static half-life of qualified melt blown filter cotton may only be about 180 days, while the half-life of low-quality filter cotton may be very short.
       Melt blown static electricity includes surface static electricity and inner static electricity of materials. The current technology generally states that water based polar melt blown materials have higher inner static electricity, higher filtration efficiency, and are less prone to decay and loss compared to ordinary melt blown materials. They can be stored and used for a longer period of time, but their prices are higher.
       At present, both official testing and amateur testing lack testing data for conventional environments, only providing less reliable reference time.
There are some amateur tests online that only provide initial filtering efficiency. For disposable masks, they are usually used for no more than 4-8 hours at a time. The problem is not too big, but as reusable filter cotton, it is still difficult to use as a basis.

       Perhaps capable individuals can test and provide test data on the usage process of KN95/KN100/KP100 (including factory time and particulate matter levels in the usage environment) during use.

       Due to the fact that the virus mainly exists in droplets (particles over 5 microns) and large aerosols (mainly cells shed over 1 micron). So, in addition to the filtration efficiency of 0.3 microns, the filtration efficiency of particles around 1 micron is also a reference efficiency. The higher the reference efficiency, the better (if the filtration efficiency of particles 1 micron and above can reach 99.7% or more, they will hardly be infected).
       The filter cotton does not need to consider disinfection and sterilization measures. Once the virus is captured, it will not fall off, and it can die within hours under the rough environment of the filter cotton. Whether the virus or particles from the filtered cotton will pass through the filtered cotton depends solely on the filtration efficiency.
       It is emphasized that the filter cotton does not need to be disinfection and sterilization or recycled. It is more IQ tax to sterilize masks or filter cotton with ultraviolet or ozone.
       Compared to the recommended 4-hour use of masks, dust masks use unidirectional filtering cotton, which is not affected by exhaled humid gases, reduces efficiency and lifespan, and does not reduce airtightness due to repeated wearing. With the same material and filtering area as masks, their lifespan can be several to ten times longer than that of unidirectional filtering masks.
        If your filter cotton has been produced for six months or even a year, the usage time can be shortened to 1/2 to 1/4; During peak periods, filter cotton can be used in two stages. In the initial stage, newer filter cotton can be used. If respiratory yang does not increase significantly after a period of use, the used filter cotton can be sealed and kept for use in low valley and low aerosol environments. Do not take any disinfection and sterilization measures on the filter cotton to avoid damaging the filter cotton structure or causing static electricity loss and reducing the filtering efficiency.