Fibrous polymers have been the part of our life since the beginning of time. The application of these materials ranges from clothing to artificial blood vessels. The surface properties of selected polymers are not always adequate so they have to be modified prior to specific application. Both deposition and functionalization is often achieved at non-equilibrium conditions using gaseous plasma. This book aims to provide basics of non-equilibrium gases suitable for tailoring surface properties of products made from fibrous polymers. The book provides the basic information about the fibrous polymers and equilibrium thermodynamics, explanations of several paradoxes typical for non-equilibrium gaseous systems, principles of electrical discharges, details on application of plasma created in different gases, particularly for oxygen, nitrogen/ammonia, hydrogen and tetrafluormethane, and plasma effects on fibrous polymers, providing new properties to materials, such as hydrophilicity, hydrophobicity, adhesion, antimicrobicity, drug release and sterility.