Diffusion

Diffusion is the most difficult air filtration mechanism to imagine or explain. Very small particles come in contact with fibers due to diffusive effects. The particles collide with air molecules and are "pushed around". This effect is called Brownian motion. Because of Brownian motion small particles don't precisely follow the airstream, but instead "vibrate" or move erraticly. This erratic movement causes the probability of the particles coming in contact with filter fibers to increase.

Related Links
• Impaction
• Interception
• Sieving