the first layer of mask
the second layer of mask
the third layer of mask
last week’s continuous orange warning of heavy air pollution has become the most attractive topic in the streets. For ordinary citizens, in addition to reducing outdoor activities, the most direct and simple means of protection is to wear protective masks and take personal protective measures
however, many people find that the white protective mask will turn black after wearing for a few days, which is shocking. Have the haze particles penetrated the protective layer of the mask? Have a lot of haze particles entered the lungs? Recently, the reporter walked into the polymer nanocomposite Laboratory of Beijing University of chemical technology and observed the haze particles on the protective mask under the electron microscope. The reporter found that the key of the protective mask is the middle layer, which can block the nano haze particles. Although the mask has turned black in appearance, the interlayer is not penetrated by haze particles
experiment
which haze particles are on the new mask
PM2.5, which means that the diameter of particles is less than or equal t2.5 microns and cannot be seen by naked eyes. But under the electron microscope, the “true face” of haze particles can be clearly observed, and the electronic microscope and energy dispersive spectrometer can not only observe the haze particles, but also quickly analyze the components. Liu Yong, associate professor and doctoral supervisor of Beijing University of chemical technology, said that the micron sized haze particles attached to the protective mask can be clearly seen by magnifying the electronic microscope and energy dispersive spectrometer 2000 times. These particles are mainly inorganic salts such as calcium carbonate, iron oxide and sulfate, and non solid aerosols can only be observed by other methods
on the morning of January 6, the reporter wore a brand-new N95 protective mask (model 3m8210) and started from Yizhuang area of South Fifth Ring Road to Beijing University of Chemical Technology located in North Third Ring Road. The experimenters broke the mask worn by the reporter, then selected the inside and outside three layers of the mask at the same position, cut it into a square about the size of the nail cap, bonded it to the observation probe of the electron microscope with special tape, and then put the probe into the chassis for observation. After magnification of 2000 times, the reporter saw that the fiber diameter of the first layer of the mask is about 17.2 microns, and the diameter of the haze particles adhering to it is about 1.2 microns. Composition analysis showed that the particles contained calcium, silicon, carbon and other elements. Liu Yong said that calcium may come from sandy soil and silicon may come from dust. The second layer of mask fiber is more dense and has smaller pores. After measurement, the diameter of the second layer of fiber is about 1 micron. The reporter saw that there are still some “leaky fish” on the fiber. They are smaller and many of them have reached the nanometer level. 1n the third layer, the diameter of mask fiber becomes thicker again, and there are fewer haze particles reaching this layer< According to Liu Yong, the protective mask can not block PM2.5 particles, but it can block most of them experiment is the mask invalid when it turns black the experimenters took out another brand-new N95 mask (3m9901v), which is common in the market, to test the protective effect in extreme environment. After half an hour, a round black area appeared on the surface of the mask. From the naked eye, there is no obvious change in the second and third layers of the mask. According to estimates, half an hour of vacuuming is equivalent to a person breathing for several months or even longer. Under the electron microscope, dense haze particles adhered to the first layer of the mask fiber, much less haze particles adhered to the second layer of the mask fiber, and less particles reached the third layer. According to the experimenters, this shows that most of the haze particles are blocked by the mask, and the protective effect of the mask is good. Therefore, when the mask turns black, there is no need to worry that the haze particles will pass through< According to Liu Yong, the most common protective masks on the market are generally composed of three layers. The outermost layer of the mask is superfine fiber, which can not block too small particles, but plays a role in shaping. The middle layer is the densest, which can block and absorb the vast majority of PM2.5 particles. The third layer is in contact with the skin. He said that at present, protective masks using nanofibers are quite common in the market. He did not recommend people to wear respirators such as "gas masks". He said that the protective effect of "gas masks" may not be better than ordinary protective masks. The protection effect mainly depends on the filtration efficiency, and the key lies in the detection, not in the complexity of the structure. For ordinary citizens, the simplest way to protect themselves in haze days is to choose masks with big brands and guaranteed quality it is suggested that the anti haze mask can be replaced in three days the engineer of 3M company told the reporter that the body of the protective mask is made of anti particulate filter material, and the fixing belt is connected with the body, so as to fix the mask on the head stably. According to the different ways of wearing, the fixed belt can be designed into headwear type, ear belt type or neck belt type, etc., which requires a certain degree of tightness to ensure that the mask is not easy to loosen when the head rotates. The metal nose clip can help to seal the nose. 1f it is too soft, it is easy to become loose during use, leading to leakage. Some masks also have a one-way exhalation valve which can only be opened when exhaling. This is to reduce the exhalation resistance, help exhaust the hot and humid air exhaled by the human body, and improve the comfort. However, the air tightness of the exhalation valve when inhaling must be good enough, and the connection between the exhalation valve and the mask body must not leak. All these need to be verified by testing. According to the corresponding certification level, the protective mask must achieve the required minimum filtration efficiency. For example, the filtration efficiency of masks meeting the Chinese national standard kn95 for non oily particles (including particles in haze) should not be less than 95% the airtightness of the protective mask is also important, because the air pollutants that can enter the mask when the mask is worn mainly come from the leakage between the mask and the wearer’s face. 1f the protective mask is not suitable for the wearer’s face, there is obvious leakage, no matter how high the filter efficiency of the mask is, it basically does not provide protection, and the air flow will automatically bypass the filter material with high resistance, Enter the mask from the leakage with the lowest resistance to make the protection ineffective. For consumers, instead of pursuing higher filtering efficiency, it’s better to choose a mask that is suitable for them and can achieve a good fit with the face and has basic protective effect. 3M engineers said that used masks are usually damp when they are just taken off, so they should be kept dry and sanitary during storage to avoid contamination or extrusion deformation of the masks. The masks can be stored in a clean paper bag. 1t is also necessary to pay attention to hygiene when reusing the mask, and avoid polluting the inner surface of the mask during removal and re wearing. 1n addition, for the folding mask, if the nose clip needs to be bent during storage, a finger pad should be used to bend the inside of the nose clip to avoid the nose clip breaking or forming a particularly sharp angle. Considering various factors, the anti haze mask can be replaced after wearing for three days