Below is a list of Air Filters manufacturers from Litchfield, Illinois. Air filters are designed by air filter manufacturers to remove a range of contaminants from the air, including molds, gases, dirt and odors. There are specific air cleaner filters available for different needs, for not all filters are designed to remove the same particles. Filter efficiency is determined by a few different factors: the size of the filter fibers, the density of the fibers in the filter and the velocity of the air that moves through the filter.