Manufacturer of Ultra-Low Resistance, Plateless, High-Efficiency Air Filters

Airborne dust particles move due to inertial motion, random Brownian motion, or the influence of some field force. When these particles collide with other objects, the van der Waals forces (forces between molecules and molecular clusters) cause them to adhere to the fiber surface. Dust entering the filter medium has more opportunities to collide with it, and upon impact, it becomes stuck. Smaller dust particles collide and agglomerate to form larger particles that settle, resulting in a relatively stable concentration of dust particles in the air. This is why indoor surfaces and walls fade.

It is a misconception to view fiber filters like sieves.

Inertia and Diffusion

Particulate dust undergoes inertial motion in the airflow. When it encounters randomly arranged fibers, the airflow changes direction, and the particles, due to inertia, deviate from their original direction and collide with the fibers, becoming stuck. Larger particles are more likely to collide, resulting in better filtration.

Small dust particles undergo random Brownian motion. The smaller the particles, the more intense the random motion, the more opportunities they have to collide with obstacles, and the better the filtration effect. Particles smaller than 0.1 micrometers in the air primarily undergo Brownian motion; 

their small size results in good filtration. Particles larger than 0.3 micrometers primarily undergo inertial motion; larger particles have higher efficiency. Particles with little diffusion or inertia are difficult to filter. When measuring the performance of high-efficiency filters, the efficiency value for difficult-to-measure dust particles is often specified.

Ultra-low resistance, plateless, high-efficiency airflow filter manufacturer

Electrostatic Effect

Due to various reasons, fibers and particles may become charged, generating an electrostatic effect. Electrostatically charged filter materials can significantly improve filtration performance. 

Reason: Static electricity causes dust particles to change their trajectory and collide with obstacles; static electricity also makes dust particles adhere more firmly to the medium.

Materials that can generate static electricity are also called "electret" materials. Even with static electricity, the resistance of the material remains unchanged, and the filtration effect is significantly improved. 

Static electricity does not play a decisive role in filtration effectiveness, but only an auxiliary one.