A first papermaking raw material for an upper layer and a second papermaking raw material for a lower layer are subjected to papermaking so as to form a filtering material with a continuous density gradient from the upper layer to the lower layer. Each of ...

The module (1) has a housing (2) having an inlet opening (3) and an outlet opening (4), where the housing forms an accommodating space (5) in which a filter element (6) is accommodated. The filter element has a filter medium (7) that is arranged in a block...

An air filter element 10 for an internal combustion engine, the air filter element 10 having a noise reduction feature comprising first and second contiguous air-permeable regions 12, 14 wherein the first region has a thickness and/or density different fro...

A large capacity HEPA filter (10) is produced in which a layered filter medium (12) unitarily formed by an upstream non-woven fabric which can remove 70 to 90 % of 0.3 mu m particle and a downstream non-woven fabric which can remove 99.9 % of 0.3 mu m part...