the particles are fused primarily to the smaller denier fibers at numerous points 28 and may also be bonded to the larger denier fibers as shown at 30 as can be seen from fig3 the filter structure is a cage like structure in which particulate matter may be entrapped and substantially precluded from migrating fusing of the particle to the individual fibers desirably is localized in that the fiber does not form a film over the particle or otherwise substantially reduce the surface area of the particle available for contact with a liquid or gas stream moving through the filter structure the particulate matter may be selected from a wide variety of substances having some function that is desirably incorporated into a fibrous structure one of the most common is activated carbon other types of functional particulate matter includes silica zeolite molecular sieve clay alumina ion exchange resin organic metal catalyst metal oxide biocide fungicide and virucide for example a fungitide particulate matter may be incorporated into a filter structure such as for an automobile climate control system to remove mildew and mildew odors from the circulated air biocides and virucides may be incorporated into filters for protection against microbial components particulate sizes may range from a small size.