Fiber filters utilize several mechanisms for aerosol collection such as inertial, gravitational setting, interception, and diffusion. Each collection efficiency depends on particle size and filtration velocity. Large particles are collected in a filter by inertial impaction at a high filtration velocity while small particles are removed from the air by Brownian diffusion. The Model 3180 controls its diffusion collection increasing filtration velocity, and collecting particles only by inertia.
