A protective mask is a kind of respiratory protective equipment for the purpose of preventing the spread of certain respiratory infectious microorganisms and protecting physical health.
1. Daily protective masks
The mask body of the daily protective mask is made of filter material, and the wearer overcomes the resistance of the filter material to the airflow by spontaneous breathing, so it is called a self-priming filter respirator. When inhaling, the low air pressure in the mask makes the air flow into the mask; when exhaling, the air pressure in the mask is higher than the ambient air pressure, and the air is discharged through the mask. When the filter material of the mask meets the requirements of the standard, and the mask is sufficiently close to the user's face, most of the inspiratory airflow will be filtered through the filter material. Daily protective masks cannot be 100% close to the face, which is affected by many factors such as the shape of the face, the smoothness of the skin, and whether there is hair under the mask. Most of the particulate matter inhaled by wearing a daily protective mask comes from leakage, so the tightness of the daily protective mask is the key to ensuring that the high-efficiency filter material works. In order to reduce leakage, daily protective masks must be designed with a three-dimensional structure, and a certain pressure is applied by the headband and nose clip to make the mask fit closely with the face.
Daily protective masks are mainly divided into two categories: dust masks and gas masks.
Dust mask: It is a mask that has the ability to protect against harmful dust aerosols. Dust masks are generally cup-shaped, which can effectively fit on the nose and mouth, so as to achieve the effect of dust prevention. Dust masks are usually used to block dust or exhaust gas and cannot filter out germs.
Respiratory masks: Respiratory protective equipment used to protect respiratory organs from toxic biological warfare agents and radioactive dust.
2. Medical protective masks
The medical protective mask is composed of a mask face and a tension belt. The mask face is divided into inner, middle and outer layers. The inner layer is ordinary sanitary gauze or non-woven fabric, the middle layer is ultra-fine polypropylene fiber meltblown material layer, and the outer layer is It is a non-woven or ultra-thin polypropylene meltblown material layer. This high-efficiency medical protective mask has strong hydrophobicity and air permeability, and has a significant filtering effect on tiny virus-carrying aerosols or harmful dust particles. The overall filtering effect is good, and the materials used are non-toxic and harmless, and are comfortable to wear. It can prevent infection caused by airborne infectious agents with a diameter of ≤5μmg or close contact (≤1m) with droplet-borne diseases. The particle filtration efficiency of the filter material of the mask should not be less than 95%, and the protection level should be high.
The scope of application includes:
Protection against the harm of suspended particles in the air to the human body
Protection for medical staff in infectious disease areas
Protection for virus laboratory personnel
Protection of various types of personnel during the epidemic of infectious diseases
Toxic chemicals, mine workers, people with pollen allergies
Individual Soldier Protection of Army Biochemical Weapons
The materials used to filter particulate matter are mineral fibers, natural fibers or synthetic fibers. There are five mechanisms by which filter fibers can filter particles in the air, and they can act comprehensively.
Sedimentation: Large particles are deposited on the filter material by gravity in the airflow and separated from the airflow;
Inertial impact: When the particles in the airflow bypass the filter fibers blocking the airflow, the higher-quality particles will deviate from the airflow direction due to inertia, hit the filter fibers and be filtered out;
Intercepting effect: The particles are located on the streamline closest to the filter material in the airflow, and the particles are "scraped" by the filter material because the radius of the particles is greater than the distance between the streamline and the filter material;
Diffusion: Affected by the thermal motion of air molecules, extremely tiny particles are impacted by air molecules, constantly changing the direction of movement, showing Brownian motion, and randomly contacting the filter material fibers and being filtered out;
Electrostatic effect: If the filter material fibers have weak static electricity, no matter whether the particles in the air flow are electrostatically charged or not, when they are close to the filter material fibers, they are easily attracted by static electricity and are filtered out. The electrostatic effect can help the filter material without increasing the airflow. Improve filtration efficiency under the premise of resistance.
