This book is devoted to a nontraditional class of materials which are manufactured by the melt-blowing process - i.e. by extrusion of polymer melt followed by fiber stretching with a gas stream. For the first time extensive data on classical and modern modifications of this technology are generalized and a review is given of extrusion head dies and subsidiary equipment. The text examines the structure and main properties of melt-blown materials as conditioned by peculiarities of overheated polymer melt spraying in an oxidizing medium. Information is given about filtering mechanisms and the main types of polymer fibrous filtering materials: electret, magnetic, adsorptional, bactericidic, and about carriers of microorganisms in biofilters. Social and ecological aspects of the application of melt-blown materials are analyzed.