Dust masks are designed to prevent dust from entering the human respiratory system. Although the structure is simple, it is not simple to use. Choosing a suitable and suitable mask is only the first step in protection. To be effective in protection, it needs to be used correctly. This not only includes wearing it according to the instruction manual to ensure that it is in the correct position every time, but also needs to be worn consistently during dust collection operations to detect in time If there is any sign of failure, replace it in time. When any part is damaged, broken or lost (such as nose clip, nose clip cushion), and when breathing resistance is obviously increased, it should be discarded. How is this dust-proof function realized? Let's take a look at the filtering mechanism of Dust-proof mask to find out.
一, Shock and inertia - surface filtration
Shock: Dust airflow close to fibers, dust with larger particle size and wind speed Particles contact or collide with each other and are intercepted by fibers.
Inertia: When passing through the curved mesh channel of the filter material, the one with larger momentum will deviate from the streamline direction due to inertia , collides with the fiber and is intercepted. For dust masks, the inertial deposition with large particle size, high density and fast speed is obvious. (Supplementary note: Momentum refers to the product of the mass and velocity of the object; particle size refers to the diameter of the particle.) 2. Diffusion—deep filtration
Collisions of dust particles with gas molecules generate random Brownian motion, which leads to random motion of the particles. When the dust-laden airflow approaches or passes through the filter material, this movement causes the particles to spread and become random with the fibers, so that they are collected (deposited) on the fiber cotton. When the wind speed is small, the diffusion deposition is obvious.
3. Electrostatic filtration
When the distance between the dust and the surface is less than or equal to the radius R, due to the gravitational force with the fiber molecules, the smaller particles are adsorbed and trapped. In other words, in the process of smashing and moving, charges will be generated due to mutual friction, and different substances will carry different polarities; those with opposite charges will form larger new particles due to mutual attraction, which are easier to be captured; on the other hand , the same dust diffuses due to mutual repulsion (Brownian motion), and is easily trapped.
According to the characteristics, positive and negative static electricity can be used as the filter material of dust mask. When the dust-laden airflow touches the filter material and continues to move forward after passing through the filter material, the positive and negative dust particles will be electrostatically captured. The greater the charge of the filter material, the higher its dustproof efficiency.
Fourth, improved filtering
Respirable dust means that all the dust particles collected are below 7.07m, and the collection efficiency of 5m is 50%. Particles with a particle size smaller than 5m that can enter the alveolar area of the human body are the cause of pneumoconiosis.
In summary, when the dust-laden airflow passes through the filter material of the dust mask, several mechanisms work together In this case, the larger dust particles are intercepted by inertia or impact, while the smaller ones are deposited by diffusion or electrostatic action, or become new large particles by electrostatic action, are intercepted, or deposited.