Generally, the filtration material used for air filters manufacturing is the filtering paper based on cellulose fibers impregnated with phenolic, epoxy or acrylic resins. The impregnation of cellulose fibres protects it from water, oil and fuel fumes. For modern materials, additions of synthetic fibres which increase filtrating efficiency and contaminants absorption are often used. Also completely synthetic filtration materials - unwoven fabrics are made, which due to its specific structure are able to trap several times more contaminants than traditional filtering paper and maintain high efficiency and low flow resistance. Particularly good results are achieved applying two, or even three ply materials, where each layer has a different structure and filtration properties. Air is filtered selectively from various size contaminants flowing through each layer. These features provide absorptivity increase and high filtering efficiency.