How to choose a face mask?

What is a face mask?

Face mask is a kind of sanitary product, which is generally used to filter the air entering the mouth and nose by wearing it on the mouth and nose, so as to block harmful gases, smells and droplets from entering and leaving the mouth and nose of the wearer. It is made of gauze or paper, etc.
Masks have a certain filtering effect on the air entering the lungs. When respiratory infectious diseases are prevalent, and when working in dust and other polluted environment, wearing masks has a very good effect.
Masks can be divided into air filter masks and air supply masks.

A brief history of the development of masks

China is the first country in the world to use masks. In ancient times, people in the court began to cover their mouths and noses with silk scarves to prevent dust and air pollution. It’s not sanitary to cover your nose with your hands or sleeves, and it’s not convenient to do other things. Later, someone used a piece of silk cloth to cover your mouth and nose. In his travels of Marco Polo, Marco Polo recorded his experiences of 17 years living in China. One of them: “people in the palace of the Yuan Dynasty used a piece of silk cloth to cover their mouths and noses.”.

  • At the beginning of the 13th century, masks only appeared in the Chinese court. In order to prevent their breath from spreading to the emperor’s food, the waiter used a kind of silk and gold thread cloth to make a mask.
  • At the end of the 19th century, masks began to be used in the field of medical care. German pathologist ledge began to recommend gauze masks for medical staff to prevent bacterial infection.
  • At the beginning of the 20th century, masks became necessary for public life for the first time. The Spanish flu that has swept the world has killed about 50 million people, and ordinary people have been asked to use masks to fight the virus.
  • In the middle and late 20th century, masks were frequently used in large scale. Masks have played an important role in preventing and blocking the spread of pathogens in the history of influenza.
  • In March 1897, medge, a German, introduced a method of wrapping the nose and mouth with gauze to prevent bacteria from invading. Later, someone made a six layer gauze mask and sewed it on the collar. When you use it, just turn it over and cover your mouth and nose. However, this kind of mask always needs to be pressed by hand, which is extremely inconvenient. Later, someone came up with the idea of strapping it to the ear, which became the mask that people often use today.
  • In 1910, the plague broke out in Harbin, China. At that time, Dr. Wu Liande, Deputy Supervisor of Beiyang Army Medical College, invented the “Wu mask”.
  • In 2003, the use and popularization of masks reached a new climax. A “SARS” almost made masks out of stock at one time. There was a long line in front of every drugstore, and people rushed to buy masks.
  • In 2009, after the “bird flu” in 2004, the “A H1N1 flu” made the mask army appear in front of the world’s major news media again.
  • In 2013, the emergence of PM2.5 air hazard concept caused the public to pay attention to air pollution, making masks and other protective equipment very popular during the haze weather.
  • On February 7, 2020, in the disinfection supply center of the Second Affiliated Hospital of Xi’an Jiaotong University, more than 30 medical staff and volunteers began to make masks with materials such as medical packaging non-woven fabric, equipment absorbent paper, N95 melt blown filter cloth, etc.

Specifications of face masks

  • Plane masks are divided into: cotton masks, non-woven masks, polymer masks, active carbon powder filter masks, active carbon fiber felt pad masks.
  • Size specification: 18 × 9 (adult), 15 × 9 (child).

Types of face masks

General thermal/decorative masks

This kind of mask is cheap and fashionable. It is made of ordinary cotton fabric. It has no isolation and protection function, but is a hotbed for bacteria breeding. It mainly plays the role of decoration and warmth preservation. It can not be used for anti infection of new coronavirus. Accordingly, it can be produced by ordinary clothing production companies. It does not belong to the medical industry The medical device does not need to apply for the medical device production license.

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General decorative mask

Labor protection mask

This kind of mask is mainly used for dustproof and harmful gas prevention during labor production. All kinds of dustproof masks, PM2.5 masks and masks with active carbon layer on the market belong to this type. It belongs to special labor protection articles. It may have a certain protective effect on the infection of new coronavirus, but it is very limited, because droplets may be attached to dust particles in the air for transmission Virus, the production of such masks requires the “production license of special labor protection articles”, which is a classification of the “national industrial product production license”, and must conform to the relevant product implementation standards.

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Labor protection mask

Medical masks: including three categories

Medical surgical mask

It is usually made of mask, shaped piece, strap and other components, and is generally made of non-woven material, which plays an isolation role through filtration. It is used to wear on the mouth and nose of the medical staff in the operating room to prevent the spread of dandruff and respiratory tract microorganisms to the open surgical wounds, and to prevent the spread of the body fluids of the surgical patients to the medical staff, so as to play a two-way biological protection role. In this outbreak of new coronavirus, it has a certain protective effect. The common blue disposable masks in pharmacies belong to medical surgical masks.

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Surgical mask

Medical protective mask

A mask made of one or more fabrics that can isolate virus aerosols, virus containing liquids, etc. Under the breath air flow, it still has the barrier function to the virus aerosol and the virus containing liquid, and when it is removed, the outer surface of the mask does not contact with the human body. The N95 medical protective mask is worn on the face of personnel in contact with virus materials in medical institutions to prevent the transmission of virus from patients to medical personnel. It has a good protective effect.

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Medical protective mask

Mask for continuous positive pressure ventilation

Used for non-invasive ventilation support such as chronic respiratory insufficiency, improvement of ventilation and sleep treatment. This is not commonly used by patients in need.
All the above three categories of medical masks belong to class II medical devices, and the production needs to go through the “medical device production license” and other relevant procedures.

Function

Use opportunity

N95 face mask

More than 95% submicron particles can be blocked. However, the respiratory impedance is high, so it is not suitable for ordinary people to wear for a long time.

Use by medical and other professionals

Surgical mask

More than 90% of the 5-micron particles that can be blocked must be replaced every day. If they are damaged or dirty, they must also be replaced immediately.

1. When there are respiratory symptoms.
2. Go to hospitals, cinemas and other closed and unventilated places.
3. When going to the epidemic area of new influenza virus.
4. Laboratory staff and livestock farm staff.

Active carbon mask

It can breathe organic gases, odorous molecules and toxic dust. If you have to breathe hard and cannot breathe peculiar smell, replace it.

1. When riding a locomotive.

2. When painting.

3. When spraying pesticides.

Cotton or gauze masks

Filter only larger particles. It can be reused after cleaning.

1. During normal cleaning work.

2. When the surgical mask is not available.

General paper mask

More than 70% of 5 micron particles can be blocked. It should be replaced every day, even if it is damaged or dirty.

NIOSH divides filter materials into the following three types:

  • 1. N series: n stands for not resistant to oil, which can be used to protect non oily suspension particles.

  • 2. R Series: R stands for resistant to oil, which can be used to protect non oil and oily suspension particles.

  • 3. P Series: P represents oil proof, which can be used to protect non oil and oil-bearing suspended particles.

“Minimum filtration efficiency of filter material” is divided into the following three grades:

  • 1.95 grade: indicates the minimum filtration efficiency ≥ 95%.

  • 2.99 level: indicates the minimum filtering efficiency ≥ 99%.

  • 3.100 grade: indicates the minimum filtering efficiency ≥ 99.97%.

Therefore, N95, R95, p95 and n99, R99, p99 with higher filtering function, and even N100, R100 and P100 masks can effectively filter suspended particles or bacteria.
In addition, the EU standard ffp1, FFP2 and ffp3 industrial masks can also effectively filter out particles or bacteria.

Standard of face mask

EU EN149 standard

FFP1 category mask Minimum filtration effect “80%
FFP2 respirator Minimum filtration effect “94%
FFP3 category mask Minimum filtration effect “97%

Australian AS1716 standard

P1: minimum filtration effect “80%
P2: minimum filtration effect “94%

Japanese MOL validation standard

According to Decree No. 0207006 promulgated by Japan in February 7, 2005, the standard of dust respirator is as follows.

Test environment condition
Experimental particle
DOP (liquid)
NaCl (solid)
Particle size distribution M
0.15-0.25
0.06-0.1
Experimental concentration [mg/m3]
Less than 100
Less than 50
Experimental flow [L/min]
Eighty-five
Eighty-five
Test time
Total supply 200mg
Total supply 100mg
Standard for replacement dust respirators
Distinguish
Filtration efficiency [%]
Inspiratory pressure below [Pa]
Exhaust pressure below [Pa]
DOP
NaCl
RL3
RS3
99.9
160
80
RL2
RS2
95
80
70
RL1
RS1
80
70
70
Disposable disposable respirator standard
Distinguish
Filtration efficiency [%]
Inspiratory pressure below [Pa]
Exhaust pressure below [Pa]
DOP
NaCl
Air valve
Air free valve
Air valve
Air free valve
DL3
DS3
99.9
150
80
100
DL2
DS2
95
70
50
70
50
DL1
DS1
80
60
45
60

45

Chinese national standard GB6223-86UDC614.894

The above inspection standards are tested in addition to the Japanese standard (0.06-0.1 micron), with a diameter of 0.3 microns. The flow rate of the EU standard is 95L/min. American Standard It’s 85L/min. The GB of our country uses more than 90% of the suspended particle size of <5 micron, more than 70% of <2 micron, and the flow value is 42.5L/min. In the detection and certification of filter materials, we adopted the idea of “worst case”, that is, setting up the test condition in laboratory is the worst condition. For example, the diameter of the ammoniated sodium salt or DOP oil mist used in the efficiency test is 0.3 micrometers in diameter, which represents the size of the particles that are very small and the most easily penetrated by the filter material, representing the amount of respiration that is carried out in strong physical labor. Before the experiment, the high temperature and high humidity pretreatment of the filter material is also required, representing the harsh working environment, all of which are for inspection. Under such harsh conditions, if the filter material can be detected to achieve the corresponding level of efficiency, then in practical applications, it will be more effective in protecting workers’ health. The filter material is usually activated carbon or chemically treated activated carbon as material to filter poisonous gas or toxic vapor through adsorption or chemical reaction without being inhaled. The internal structure of activated carbon has a lot of micropores to form a large specific surface area. These micropores can absorb toxic vapors and toxic molecules of different sizes without escaping. Activated carbon processing and installation requirements are very high, if improper handling or activated carbon particles are coarse, resulting in gaps between particles, then the gas will penetrate through the gap into the respiratory tract, and will not be adsorbed. Therefore, the replacement of bagged activated carbon is very unscientific. The active carbon in a good chemical filter box should be packed densely, with a small particle size and large specific surface area. This will only lead to a long time to prevent the toxin, and at the same time, we should also consider breathing resistance and wear comfort.

Materials for making face masks

  • 2-layer mask: non-woven fabric, nose rib, ear hook.
  • 3-layer mask: non-woven fabric, nose rib, ear hook, filter paper.
  • Active carbon mask: non-woven fabric, nasal tendon, ear hook, filter paper, active carbon filter paper.

Use of face masks

  • 1. General mask or gauze mask: it can only filter large particles and is only suitable for normal cleaning work.
  • 2. Surgical mask: it can block more than 90% of 5 micron particles, and should be replaced every day, but it should be replaced immediately if it is damaged or dirty. It is suitable for use when there is a cold, fever, cough and other respiratory symptoms, or when going to the hospital cinema and other places without wind
  • 3. Active carbon mask: it can absorb organic gas and toxic dust without sterilization function. It should be replaced immediately if it needs to breathe hard or cannot absorb peculiar smell. It is suitable for painting or pesticide spraying.
  • 4. N95 mask: it can block 95% of the last micron particles, and has high respiratory impedance. It is not suitable for ordinary people to wear it frequently, and it should be avoided to be reused.

Disposable mask vs disposable surgical mask

Because disposable masks and disposable surgical masks are the kind of masks that we remember doctors in traditional Chinese medicine hospitals wearing, so I put them together. You may be thinking, since it’s a kind of mask, why divide a mask into two names? In fact, disposable masks are not equal to medical surgical masks. Many people think that disposable masks are medical surgical masks, which is a big misunderstanding. Disposable masks are not equal to disposable medical surgical masks.

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Disposable mask and disposable medical surgical mask are made of three layers, the biggest difference is the middle layer. The medical surgical mask is melt blown non-woven fabric, with 95% filtration rate in terms of bacteria filtration efficiency, but disposable mask can not filter particles and prevent blood penetration. The disposable surgical mask can have a filtration efficiency of more than 30% of non oil particles and prevent blood penetration. Both disposable masks and disposable surgical masks can prevent bacteria, but disposable masks can not prevent haze and blood.

Precautions for use of mask

Duration of use

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 – 7 ℃ is inhaled into the lungs through the nose, the air flow has been heated to 28.8 ℃, 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.

Cleaning and maintenance

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.
Masks should be cleaned and disinfected every day. Both gauze masks and air filter masks can be disinfected by heating. The specific methods are as follows:

  1. Cleaning. First, gently rub the gauze mask with warm water and soap. The bowl shaped mask can be gently cleaned with a soft brush dipped in detergent, and then washed with clean water. Please note that do not rub hard, because if the gap between warp and weft of gauze is too large, it will lose the function of preventing flying foam.
  2. Disinfection. Soak the cleaned mask in 2% Peracetic Acid Solution for 30 minutes or boil it in boiling water for 20 minutes or steam it in a steamer for 15 minutes, then dry it for standby. This method is suitable for gauze masks and bowl masks.
  3. Check. Before reuse, it is necessary to carefully check whether the mask and mask are still in good condition. For gauze mask and mask, light transmission inspection method can be adopted, i.e. take care of them before getting the lamp to see if there is any obvious light spot, and whether the light transmittance of the middle part and the edge part is the same. If there is any doubt, replace them with new ones. In any case, masks and masks should be renewed after 3 to 7 times of cleaning. Masks with excellent quality can be cleaned 10 times. The active carbon adsorption respirator should be replaced regularly. If the active carbon interlayer is not replaceable, it should be replaced after 7 to 14 days. This kind of respirator can not be reused after cleaning.

Properly handle

Daily use of masks should be handled properly. Masks used by patients or in the process of care should be placed in a lined container in the patient’s room for further treatment.

How to choose a face mask?

In terms of design, if the priority is given to the protection ability of the wearer (from high to low):
N95 mask > surgical mask > common medical mask > common cotton mask.

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Ranking of the priority of different masks for the protection ability of the wearer

Recently, we have seen good multimedia reports that many large pharmacies sell masks that do not meet the standards. There are even businesses that sell labor protection masks for dozens of yuan. When you buy masks, you must see the standards on the mask packaging clearly, and don’t be confused by the words on the mask packaging and the description of the businessmen. No matter when buying masks, we need to pay attention to choosing larger brands. Some small brands may reduce costs or even the output of unqualified health masks, which undoubtedly increases the risk for our common people.

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If it is anti haze, it is recommended to use medical protective mask or special anti haze mask, and it is recommended to wear glasses with exhalation valve. The medical protective mask has the highest level of protection, but it is disposable. The cost of preventing haze for a long time will be higher. The anti haze mask with inner core can be more suitable. It is important to remember that disposable masks and cotton masks do not prevent haze. Although the medical surgical mask can prevent haze, but the filtering efficiency is only 40%, it is not recommended to wear it.

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Anti haze mask

If it’s for medical use, anti-virus and spray spread disposable masks, medical surgical masks and medical protective masks can be used, and their bacterial filtration efficiency is very small. Disposable mask can not prevent blood penetration, so it is not allowed to use disposable mask in the way of preventing blood penetration. It is necessary to use medical surgical mask or protective mask.

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If it is the medical staff who are in close contact with the serious infectious virus, they need to use the medical protective mask. Because it requires long-term close contact with the virus, it is necessary to use the highest level of protection (kn100, N100, ffp3) without any mistakes. We ordinary people, as long as we don’t contact the virus for a long time, can use medical surgical masks. Of course, if you have a lot of money, the higher the level of respirator, the better. In the period of virus control, no matter what mask you wear, it’s better than no mask.

We also have a question that there are two kinds of respirators: respirator with or without exhalation valve. Which is the best choice? First, it is as like as two peas to make sure that the efficiency of the air valve is exactly the same as that of the air valve. The function of exhalation valve can only exhale outwards but not inwards. In winter, outdoor activities with exhalation valve are very friendly to the spectacles party, which can greatly reduce the condensation of the hot breath and the cold glasses. In the process of virus prevention and treatment, if the respirator with exhalation valve is worn by the patient, the virus can be exhaled from the respirator. It is not recommended that the patient have the respirator with exhalation valve. Moreover, there is a physical structure in the respirator with exhalation valve. If the exhalation valve is damaged, it may cause air leakage when inhaled, so it is better to wear the respirator without exhalation valve in extreme scenes. Because of the physical design, the leakage rate of the protective mask is lower than that of the medical surgical mask, that is to say, it has a better fit and tightness with the face.
Pay attention to the service life of the mask:
In addition to the use scenarios and filtering efficiency of the four masks mentioned above, we also need to pay attention to the service life of the masks. The four kinds of masks commonly seen on the market have service life. The specific service time is different for different types and brands of masks. We can find them on the outer packaging of masks. It should be noted that no matter disposable mask, disposable surgical mask or medical protective mask can be cleaned or disinfected. Cleaning or disinfecting will lead to the decrease of filtration efficiency. It’s not believable that disposable masks can be used repeatedly after being heated, so it’s suggested that the masks should be replaced strictly according to the use time on the mask package.

How to wear the mask correctly?

Medical protective mask > medical surgical mask > disposable mask > cotton mask. As long as you know that you have selected the corresponding mask in your use scenario, it is more important to wear the mask correctly. Even if your mask has a higher level of protection, it doesn’t work as long as the air leaks.

How to distinguish the front and back of the mask?

With the development and progress of industrial costs, the impact on the environment is becoming more and more serious. More and more people are beginning to be affected by the adverse climate. They feel the suffocation of going out, and they also start to use various protective means to protect themselves. Masks have also become the main tools used by people. How to distinguish the positive and negative aspects of masks?

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Respirator is a kind of protective tool that plays a filtering role. The use of respirator plays a very good role in protecting people. In general, multi-layer filtering device will be used in respirator, so as to filter out the air pollution gas and small particles, so as to better protect people’s respiratory tract, make people’s body more safe and healthy, which also makes the use of respirator more severe Yes. To prevent novel coronavirus infection pneumonia, it is useful to choose disposable medical masks and medical respirators.
The front and back face of the mask are distinguished by metal strips. Generally, the color of the medical mask is mostly the same, which makes it difficult for people to distinguish. Generally, the metal strip is on the top and the protruding side is on the outside, and the opposite side is on the inside. At the same time, it can also be distinguished by the crease. The upward side of the crease is on the inside, and the reverse is on the outside.

How to wear the mask:

  1. Wash: first of all, clean hands to avoid unclean hands polluting the inner surface of disposable medical mask;
  2. Hang: stick the disposable medical mask on the face, mouth and nose, and hang the ropes at both ends on the ears with both hands;
  3. Pull: as shown in the figure below, open the wrinkles of disposable medical mask with both hands up and down at the same time, so that the mask can completely cover the mouth, nose and chin;
  4. Press: finally, press the metal strips on both sides of the nose of disposable medical mask tightly with the index finger of both hands, so that the upper end of the mask can be close to the nose.

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Precautions for wearing mask:

  • 1. Disposable medical mask has two sides of white and blue, one side of white is facing in and the other side of metal strip is facing up. First, tie the two straps on the lower side behind the neck and tighten them! Make the lower edge of disposable medical mask reach the root of chin;
  • 2. Pull up the upper edge belt of disposable medical mask, cover the mouth and nose with the mask, and pull the two upper straps to the back of the ear and fasten them to the head, not to the ear.
  • 3. Press the metal wire of the upper part of the nose root of the disposable medical mask with two index fingers to make it close to the nose skin, and then move the food to both sides gradually, which is the whole disposable medical mask close to the face skin.

How to remove a face mask?

Disposable face masks should be used once and then thrown in the trash. You should also remove and replace masks when they become moist.

  • Clean your hands with soap and water or hand sanitizer before touching the mask. Avoid touching the front of the mask. The front of the mask is contaminated. Only touch the ear loops/ties/band.Follow the instructions below for the type of mask you are using.
  • Face Mask with Ear loops: Hold both of the ear loops and gently lift and remove the mask.
  • Face Mask with Ties: Untie the bottom bow first then untie the top bow and pull the mask away from you as the ties are loosened.
  • Face Mask with Bands: Lift the bottom strap over your head first then pull the top strap over your head.
  • Throw the mask in the trash. Clean your hands with soap and water or hand sanitizer.

Why can masks stop the spread of the virus? What kind of material is it?

We usually say that the mask is made of non-woven fabric. Compared with textile fabric, non-woven fabric is made of directional or random fibers.
Specifically to the mask, its raw materials are all polypropylene (PP), medical masks are generally multi-layer structure, generally referred to as SMS structure.

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SMS structure

Chemistry knowledge

Polypropylene: the English name is polypropylene, abbreviated as PP, which is a colorless, odorless, nontoxic and translucent solid substance. It is a polymer formed by the polymerization of propylene. The molecular formula is – [CH2CH (CH3)] n -. Polypropylene is widely used in the production of fiber products such as clothing, blankets, medical devices, automobiles, bicycles, parts, transportation pipelines, chemical containers, etc., as well as food and drug packaging.

The non-woven fabric made of polypropylene non-woven fabric can be used for disposable surgical clothes, sheets, masks, covers, liquid absorption pads and other medical and health products. Among them, the non-woven fabric mask is made of two layers of fiber-optic non-woven fabric, which is used for medical and health care. In the middle, a layer of filter and anti bacteria cloth with more than 99.999% of the filter and spray cloth is welded by ultrasonic.

The main respirators that can play the role of virus protection are surgical masks and N95 masks. According to the technical requirements for medical surgical masks (YY 0469-2004), the important technical indicators of medical surgical masks include filtration efficiency, bacterial filtration efficiency and respiratory resistance
Filtration efficiency: under the condition of air flow (30 ± 2) l / min, the filtration efficiency of sodium chloride aerosol with median diameter (0.24 ± 0.06) μ m in aerodynamics is not less than 30%;
Bacterial filtration efficiency: under specified conditions, the filtration efficiency of Staphylococcus aureus aerosol with an average particle diameter of (3 ± 0.3) μ m shall not be less than 95%;
Respiratory resistance: under the condition of filtration efficiency flow, the inspiratory resistance shall not exceed 49pa, and the expiratory resistance shall not exceed 29.4pa.
Among them, the second standard is to ensure the bacterial filtration effect. The filtration efficiency of Staphylococcus aureus bacterial aerosol is not less than 95%, which is the origin of the concept of N95. Therefore, although N95 mask is not a medical mask, it can meet the filter efficiency of 95% and better fit the human face, so it can also play a good role in virus prevention.
The main material that brings virus filtering effect to these two kinds of masks is the inner layer filter cloth with extremely fine and static electricity – melt blown non-woven fabric.
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Melt blown nonwovens

The main material of melt blown non-woven fabric is polypropylene, which is a kind of ultra-fine electrostatic fiber cloth and can catch dust. When the droplets containing pneumonia virus are close to the melt blown non-woven fabric, they will be electrostatic adsorbed on the surface of the non-woven fabric and cannot be penetrated.
This is how the material insulates against germs. When the dust is caught by the superfine electrostatic fiber, it is not easy to be separated by cleaning, and water washing will also destroy the electrostatic dust collection ability. So the mask can only be used once. Suitable for flat face mask: ordinary grade, bfe95 (filter efficiency 95%), bfe99 (filter efficiency 99%), vfe95 (filter efficiency 99%), pfe95 (filter efficiency 99%), Kn90 (filter efficiency 90%).
Medical surgical masks are generally made of three layers of non-woven fabric. The material is spunbond + melt blown + spunbond. One layer of staple fiber can also be used to improve the skin touch, that is, ES hot-rolled non-woven fabric + melt blown non-woven fabric + spunbond non-woven fabric. The outer layer of the mask is designed to prevent flying foam, filter in the middle layer and absorb moisture in the memory. Generally, 20 g melt blown cloth is used.
The N95 cup mask is composed of needled cotton, melt blown cloth and non-woven cloth. The melt blown cloth usually weighs 40g or more, plus the thickness of needled cotton, so it looks thicker than the flat mask in appearance, and its protective effect can reach at least 95%.
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Several layers of masks are not specified in the national standard GB / T 32610. If it is a mask for medical use, it should be at least three layers, that is, SMS (two layers of S and one layer of M). At present, the highest number of layers in China is 5 layers, that is smmms (two layers of S and three layers of M). It is not difficult to make a mask. It is more difficult to make smmms cloth. The price of an imported non-woven equipment is more than 100 million yuan.

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Schematic diagram of blocking effect of SMS structure on various substances

In this case, s represents spunbond, whose fiber diameter is relatively thick, about 20 microns (μ m). The main function of two layers of s spunbond is to support the entire non-woven fabric structure, which has little effect on barrier.
The most important part of the mask is the barrier layer or melt blown layer m (meltblown). The fiber diameter of the melt blown layer is relatively small, about 2 microns (μ m), so it is only one tenth of the diameter of the spunbond layer, which is very important to prevent bacteria and blood from penetrating.
If there are too many s-spunbond layers, the mask will be hard, and if there are too many melt blown layers m, it will be difficult to breathe. Therefore, the isolation effect of the mask can be judged from the difficulty of breathing. The more difficult it is to breathe, the better the isolation effect. However, if the m-layer becomes a film, it will be basically airtight. The virus is blocked, but people can’t breathe. So this is also a technical issue.
In order to better illustrate the problem, we will make a comparison between spunbond layer s fiber, melt blown layer m fiber and hair as follows: 1 / 3 of hair diameter is close to spunbond layer fiber, and 1 / 30 of hair diameter is close to melt blown layer m fiber diameter. Of course, researchers are still developing finer fibers to ensure better antibacterial barrier.

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Diameter comparison of hair, spun viscose fiber and vinylmelt blown fiber

As mentioned earlier, the finer the m layer, the more it can block the entry of bacteria and other micro particles. For example, N95 means that under normal conditions, it can block 95% of the micro particles (0.3 μ m).

From the above explanation, N95 is actually a five layer mask made of polypropylene non-woven smmms, which can filter 95% fine particles.

Specific production process of medical mask

Production of medical mask

This is a common medical mask, mainly composed of three layers of non-woven fabric. The inner layer is ordinary non-woven fabric; the outer layer is non-woven fabric with waterproof treatment, which is mainly used to isolate the liquid emitted by patients; the middle filter layer is polypropylene melt blown non-woven fabric with electret treatment; after the final production, it shall be sterilized with ethylene oxide and kept for 7 days to volatilize toxicity, sealed and packed for transportation.
The core material of medical mask is polypropylene melt blown non-woven fabric after electret treatment. Please remember these two key words, because this is the key to filter the new coronavirus aerosol.

Raw material: polypropylene (PP) particles

I’m not going to talk about how crude oil turned into polypropylene in refineries. As long as you know, Sinopec, PetroChina and CNOOC’s refining and chemical plants will never shut down during the new year, in addition to inspection and overhaul, to ensure that our gasoline and diesel, chemical raw materials (polyethylene, polypropylene) and other continuous production will not be cut off, which is also the responsibility of the central enterprise (of course, private enterprises are not willing to shut down, because the shut down will delay production, delay making money).

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The polypropylene particles produced from the chemical plant grow like this. Most of the plastic kettles and tableware we buy are made of polypropylene.
How much is polypropylene? The current futures price is 7000 yuan / ton. A large truck can pull about 30 tons, so it costs about 200000 yuan to pick up a car of polypropylene through logistics.

Production of polypropylene fiber

Just as textile needs plant fiber, non-woven production also needs fiber material. Polypropylene particles are used to melt and shape, while high melting refers to polypropylene fiber material, which is the core raw material for the production of masks, which is the following one by one polypropylene fiber.
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In 2019, China’s domestic production of polypropylene fiber is about 1.7 million tons, including 950000 tons of high melting polypropylene fiber which can be used for masks. The production units include Zhenhai Refining and chemical, Shanghai Secco, Jingmen Petrochemical, Hainan refining and chemical, Maoming Petrochemical, Shijiazhuang refining and chemical, Guangzhou Petrochemical and so on. There are also a number of PetroChina refineries, which I am not familiar with.
In response to the epidemic, some refineries of Sinopec have begun to adjust their production plans. In February, they will continue to increase the production of HDPE fiber materials. Dushanzi Petrochemical is also on standby for adjustment. Therefore, this part of materials is mainly insufficient in inventory. After the production capacity comes up, the raw material supply of PP fiber is absolutely sufficient, as long as the road continues.
Non woven fabric manufacturers need to purchase polypropylene fiber from distributors or chemical plants as raw materials, so the logistics road is not broken. If the city road closure of non-woven fabric manufacturers means that the supply of raw materials is cut off, how to produce?
How much is polypropylene fiber? The retail price found on Alibaba is 10000 yuan / ton, and the order of magnitude is not bad. There are major central enterprises, polypropylene fiber will not be out of stock, the price will not skyrocket, you can rest assured.

Production of melt blown nonwovens

Melt blowing is a polymer extrusion nonwovens process. It was developed by the U.S. Navy in 1954 to collect radioactive particles produced by nuclear test. Then around 1965, Exxon, 3M and other companies manufactured the first generation of melt blown nonwovens.
The process principle is to draft the polymer melt fine flow extruded from the spinneret hole of the die head with high-speed hot air, so as to form the microfiber and agglomerate it on the condensing net curtain or roller, and then make the nonwovens by self adhesion. The principle of spinneret is as follows:
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The melt blown material is made by hot melting of its own fiber. The non-woven fabric produced by the melt blown method with thicker thickness is randomly arranged with interlayers, forming a multi bend channel structure of the melt blown material, so that the particles (new coronavirus aerosol) will collide with the fiber and be retained.
Key points: the filtering mechanism of medical mask is Brownian diffusion, interception, inertial collision, gravity sedimentation and electrostatic adsorption. The first four are all physical factors, that is, the non-woven fabric produced by melt blown method has the natural characteristics, with the filterability of about 35%; this is not up to the requirements of medical masks, we need to carry out electret treatment on the materials, make the fibers charged, and use static electricity to capture the AIR-SOLUBLE glue where the new crown virus is located.

Electret treatment

Electrostatic adsorption is the capture of new coronavirus droplets (aerosols) through the Coulomb force of charged fibers. The principle is to make the surface of the filter material more open, capture the particles, and increase the charge density, so the adsorption and polarization effect of the particles is stronger. Therefore, the melt blown non-woven filter material of the filter layer must undergo electret treatment to achieve 95% filterability without changing the respiratory resistance, so as to effectively prevent the virus.
The respirator shall ensure comfortable ventilation while reaching the barrier effect. The suction resistance of medical respirator shall not exceed 343.2 Pascal (PA), and that of civil respirator shall be less than 135 Pascal (PA).
Electret treatment can greatly improve the filtration efficiency without changing the respiratory resistance, and the higher the electret voltage is, the higher the material filtration efficiency is. Generally, the voltage of the electret should be between 30KV and 60kV, and the time of electret should be more than 20 seconds.
Finally, the medical high melting finger melt blown non-woven fabric material is produced, which is about 20000 yuan / ton.

Production line of masks

To solve the problem of raw materials, mask production is just a problem of piling up workers and materials and maintaining production line capacity. This is very fast. It’s all automated production lines. 18.5 in case of a mask machine, 100 masks can be produced per minute, and the 24-hour production capacity without shutdown is 144000 masks per day.
A small mask factory may need 10 people. The equipment includes a mask forming machine, a mask pressing machine, a mask trimming machine, a breath valve punching machine, a nose beam line laminating machine, an ear belt spot welder, a breath valve welding machine, etc. the total investment is estimated to be 500000 yuan. However, it takes 60 days for the equipment to arrive.

Ethylene oxide disinfection

If it’s a normal mask, it doesn’t need to be sterilized, but for medical use, it needs to be sterilized by the manufacturer with EO disinfection cabinet. Put the mask in 400mg / L ethylene oxide environment, use alkylation to act on the hydroxyl, make the microorganism macromolecule lose activity, and achieve the goal of sterilization.
However, ethylene oxide is not only flammable and explosive, but also toxic to human body. Therefore, it needs to be kept for 7 days for analysis after detoxification. Only after the EO residue is lower than the required value, can it be packaged and delivered to medical staff.
Therefore, the production of medical mask units, the need to have a “medical device business license” ah!
Therefore, the manufacturer of the mask needs to send the mask to the Quality Supervision Bureau for inspection, meeting the requirements of national standard gb18279.1-2015 and international standard iso11135:2014, because ethylene oxide is also a carcinogen.
Therefore, all over the industry and commerce departments to crack down on fake masks ah!
Make a point:
Only the medical mask produced according to the above process, the filter material produced by melt blown non-woven fabric with high melting finger, the electrostatic absorption increased by electret treatment, the product was sterilized with ethylene oxide and the ethylene oxide was analyzed after 7 days, it is qualified, safe and can be used to isolate the transmission of new crown virus.
Therefore, the UV disinfection, dry steaming and wet steaming, which are popular in the market, destroy the static electricity and fiber structure of the filter layer, and reduce the filtering performance to 35%.
That is to say, the use of sun anti-virus masks to continuously absorb the water vapor exhaled by people will also cause the charge loss of the filter layer, the electrostatic absorption capacity will be reduced to zero, and the filtering effect will return to about 35%. Does it work for the general public? That must be better than nothing.
But does it work for medical staff?
Useless. So if the medical staff make their own masks, it is basically equivalent to only wearing casual clothes to fight with the enemy (virus).
But do we have to throw away the masks that ordinary people use once? In fact, unless you go to a densely populated area such as a hospital or supermarket, or you need to remove the suspected or confirmed patients, if the ordinary people just go out to buy a dish, there is no one within two meters in the open environment, 15 minutes later, they go home to pick it up, use it three or five times, the cumulative time is no more than 4 hours, there is no problem at all. This can also reduce the consumption of masks.

When should I wear a mask?

Paramedics – when in contact with patients.
People – when they cough, sneeze, or visit a doctor.
In general, healthy people do not need to wear masks.
In case of an epidemic, you need to wear a mask when you go out.

Why should sick people wear masks?

Avoid infecting others with your own droplets – most of them can be blocked by the mask filter when they leave your mouth or nose.
Weak resistance when sick – avoid infection with other pathogens.
People with fever, cough or sneeze should wear masks, which is a good habit to protect others’ health.

Why can wearing masks prevent infectious diseases?

Avoid infecting others with viruses or bacteria.
Easily spread pathogens when coughing and sneezing.
Wearing a mask can reduce spray spread.
Avoid being infected with viruses or bacteria.
The mask has the function of filtering dust, droplets and other particles.
Different masks have different filtering efficiency and use.
Masks are mainly used to prevent diseases transmitted by air or droplets.
Masks are not a panacea to prevent disease transmission.
The most important thing to prevent diseases is to pay attention to personal hygiene.

Summary
how to choose a face mask - How to choose a face mask?
Article Name
How to choose a face mask?
Description
When you buy masks, you must see the standards on the mask packaging clearly, and don't be confused by the words on the mask packaging and the description of the businessmen.
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