Electrostatically charged fibers act like tiny magnets to attract and capture particles that can pass right through fiberglass filters. The air in our homes contains millions of tiny particles. A filter removes particles from the air when a particle collides with the filter media and sticks. The more times air passes through the filter, the more opportunity the filter has to capture particles. In time, the air contains fewer and fewer particles, thus becoming cleaner and cleaner.
Pleats increase the amount of media in the frame of the filter.
More media means more surface area where particles can be captured. If a filter is left in too long, it will become clogged and the airflow through it will be reduced, reducing the air coming out of the registers. Because of the reduced airflow through the heat exchanger, less heat is transferred out of the heating chamber of your furnace. The heating chamber cools quickly, and the cycle starts over again. Atmospheric dust usually contains soot and smoke, silica, clay, decayed animal and vegetable matter, organic materials in the form of lint and plant fibers.