How to select and use masks
Selection of masks
1. Masks are not suitable for people
1) People with difficulty in heart or respiratory system (such as asthma and emphysema)
3) Dizziness, dyspnea and skin sensitivity after wearing
2. What are the characteristics of several kinds of masks on the market?
Advantages of cotton mask: it can be used repeatedly,
Disadvantages: there will be saliva in the part of the mask that contacts the nose and mouth. If it is not cleaned frequently, it is easy to breed bacteria and does not meet the requirements of health. Cotton masks usually have coarse fibers, which can not effectively filter small particles, and most of them fail to pass the international safety certification, so the protection effect is not guaranteed. Gauze mask is almost useless, and the air leakage on both sides of nostril is too large.
N95 mask: it is used to avoid the infection of people wearing it; it is impossible to prevent patients from infecting others with the virus.
Surgical mask: Although the effect of avoiding infection is not as good as N95, it can prevent patients from infecting others with the virus.
3. Is the smaller the dust, the more difficult it is to be filtered by the mask?
We generally think that the smaller the dust is, the more difficult it is to be filtered, but this is a specious concept. In terms of filtration theory, there are mainly five ways to filter the dust:
1) Brownian diffusion the smaller the particle, the stronger the effect.
2) Intercept - the larger the particle, the better.
3) Inertia impact - the larger the particle, the better the effect.
4) The bigger the particle, the better the effect of gravitational attraction.
5) Static -- the smaller and lighter the particles, the more attractive they are.
It can be seen that the smaller the dust, the stronger the 1 and 5 effects, and the greater the dust, the better the 2, 3 and 4 effects, so the smaller the dust is, the more difficult it is to filter. The most difficult particle to be filtered is called MPPs (most penetrating particle). The size of MPPs is generally 0.3 μ m (the other is 0.6 μ m). MPPs is used to test the certification standards of European en149, American NIOSH and Australian as1716. As long as you buy certified masks, they can protect your respiratory system health.
4. How to choose the right mask?
There are three principles for the selection of masks:
First, the efficiency of the mask. The efficiency of the respirator is based on the efficiency of the respirator against the fine dust, especially the respirable dust under 5 microns. Because this particle size dust can directly enter the alveoli, which has the greatest impact on human health. In general, gauze masks, the principle of dust prevention is mechanical filtering, that is, when the dust collides with gauze, it will block some large particles of dust in the sand cloth through layers of barriers. However, for some fine dust, especially dust less than 5 microns, it will pass through the mesh of gauze and enter the respiratory system. At present, there are some dust masks in foreign countries. The filter material is composed of fibers filled with permanent static electricity. The respirable dust less than 5 microns is attracted by static electricity and absorbed in the filter material to catch the fine dust in the process of passing through the filter material, which really plays a role of dust prevention.
Second, how close the mask is to the shape of the face. Air, like water, flows first where there is little resistance. When the shape of the mask is not close to the face, dangerous substances in the air will leak in from the close place and enter the respiratory tract. Well, even if you choose the best filter. It can't protect your health.
Third, comfortable to wear. It requires small respiratory resistance, light weight, hygienic wearing and convenient maintenance.
Use of masks
1. Use of general masks
The mask must be the right size and wear in the right way for it to work. Masks on the market are generally divided into rectangular and cup-shaped. The rectangular mask must have at least three layers of paper structure to have a protective effect. The user should press the wire on the nose bridge of the mask, and then spread the whole mask along the nose bridge, so as to play the role. Let the child wear a rectangular surgical mask, because it has no fixed shape, if well tied, it can close to the child's face. Cup masks should be made sure that the density is enough after the mask is attached to the face, so that the exhaled air will not leak out. When wearing the cup-shaped mask, you can try to blow with your hands covered by the mask to check whether there is air leakage from the edge of the mask. If the mask is not tightly covered, you need to readjust the position before wearing it.
2. How to wear the mask correctly
1) Place the mask in the palm, place the nose metal strip towards the fingertip, and let the headband hang down naturally.
2) Put on the mask, with the metal strip on the nose upward and close to the face.
3) Place the upper headband of the mask behind the head, then pull the lower headband over the head, put it behind the neck, and adjust it to a comfortable position.
4) Press the fingertips of both hands along the metal strip of the bridge of the nose from the middle to both sides, and then press them inward slowly until they are close to the bridge of the nose.
5) Cover the mask with both hands as much as possible and conduct positive and negative pressure tests. Positive pressure test: cover the mask with both hands and exhale vigorously. If the air overflows from the edge of the mask, i.e. it is not worn properly, adjust the headband and nose metal strip again; negative pressure test: cover the mask with both hands and exhale vigorously. The center of the mask will sink. If air enters from the edge of the mask, it is not worn properly. Adjust the headband and nose metal strip again.
6) Function of breathing valve: in hot and humid working environment with poor ventilation or large labor volume, the use of respirator with breathing valve can help you feel more comfortable when exhaling. The function principle of the breathing valve is to blow the valve plate open under the positive pressure of the exhaust gas when exhaling, so as to quickly exhaust the exhaust gas in the body and reduce the sense of stuffy heat when using the mask, while the negative pressure will automatically close the valve when inhaling, so as to avoid the pollutants absorbed into the external environment.
3. When to replace the mask
1) The mask is contaminated, such as blood stains or droplets and other foreign matters;
2) The user feels that the respiratory resistance increases;
3) The mask is damaged.
4) Dust proof filter cotton: when the mask and the user's face are well closed, when the user feels a great respiratory resistance, it means that the filter cotton is full of dust particles and should be replaced.
5) The anti gas filter box, when the mask and the user's door are well sealed, should be replaced when the user smells the poison.
4. Masks should not be worn for a long time
From the point of view of human physiological structure, because the blood circulation of nasal mucosa is very strong, the passage in the nasal cavity is very zigzag, and the nasal hair forms a filter "barrier". When the air is inhaled into the nostril, the air flow forms a vortex in the zigzag channel, which makes the air flow in the nostril heated. Tests have shown that when cold air at minus 7 degrees Celsius is inhaled into the lungs through the nose, the air flow has been heated to 28.8 degrees Celsius, which is very close to the temperature of the human body. If the mask is worn for a long time, the nasal mucosa will become fragile and lose the original physiological function of the nasal cavity, so the mask cannot be worn for a long time. Masks can only be worn in special environments, such as in places where there are many people and the air is not circulating. Of course, it is necessary to wear a mask when walking in the wild, in order to resist sand and cold, or in the environment with air pollution, but the time should not be too long. In addition, masks should be worn in public places where there may be a large number of pathogens during the flu season. Wearing a mask is only one of the ways to prevent respiratory infectious diseases. The most important thing is to keep good living habits.
5. Cleaning of masks
The outer layer of the mask often accumulates a lot of dust, bacteria and other pollutants in the outside air, while the inner layer blocks the exhaled bacteria and saliva. Therefore, the two sides cannot be used alternately, otherwise, the dirt on the outer layer will be inhaled into the human body when it directly clings to the face, and become the source of infection. When the mask is not worn, it shall be folded and put into a clean envelope, and the side close to the nose and mouth shall be folded inward. Never put it into the pocket or hang it on the neck. If the mask is wetted by the exhaled heat or saliva, its function of blocking bacteria will be greatly reduced. Therefore, it is better to prepare several masks at ordinary times, so as to replace them. They should be changed and washed once a day. Wash with boiling water for 5 minutes first, then gently scrub with hands, wash with clear water and expose to the sun. But activated carbon filtration and disposable do not need to be cleaned.
6. Size of mask
After wearing, it should be able to cover most of the area below the mouth, nose and orbit, generally 13 cm wide and 17 cm long. If the mask is too small, germs, dust and dirt are easy to enter from the edge of the mask or the gap between the two sides of the nose, affecting the filtering effect of the mask. The filter function of the mask is focused on the nose, because the mouth is usually closed when people don't speak, but when someone wears the mask, his nostrils are exposed to the outside of the mask in order to breathe freely, which loses the "barrier" function of the mask to protect the respiratory tract.
How to wear N95 mask correctly:
1. Run the headband every 2-4 cm, put your hand through the mask headband, and move the metal nose forward.
2. Put on the mask and keep it close to the face. Put the upper headband behind the head, then pull the lower headband over the head, put it behind the neck, and adjust it to a comfortable position.
3. Press the fingertips of both hands along the metal strip of the bridge of the nose from the middle to both sides, and then press them inward slowly until they are close to the bridge of the nose.
4. Cover the mask with both hands as much as possible and conduct positive and negative pressure tests. (positive pressure test: cover the mask with both hands and exhale vigorously. If the air overflows from the edge of the mask, i.e. it is not worn properly, adjust the headband and nose metal strip again; negative pressure test: cover the mask with both hands and exhale vigorously. The center of the mask will sink. If air enters from the edge of the mask, it is not worn properly. Adjust the headband and nose metal strip again.)
Characteristics of various masks:
1. Respirator (N95): it conforms to the national occupational safety and Health Association standard (NIOSH) N95 approval. It is a filter separated particle with a diameter as small as 0.3 μ M. In the test, 95% of the particles with a diameter of 0.075 μ m were isolated. The diameter of coronavirus pneumonia (SARS) virus is about 0.1 to 0.12 μ M.
2. Surgical mask: it is made of three layers of "non woven", which is suitable for operating room environment; it can block particles with a diameter of more than 4 microns.
3. Active carbon medical mask: the main function of the added active carbon material is to prevent odor, not bacteria and virus, and the respiratory resistance will increase, with the function of bacteria isolation of 98%.
4. Dust mask: it is mainly dust-proof and has general anti bacteria function.
5. Ordinary paper mask: it is useful to block large particles. Viruses less than 5 microns in diameter can easily pass through and have limited bacteria isolation function.