Abstract: A filter material fabricated by mixing 10 to 30% by mass of first fibers having a fiber diameter of 10 to 40 ?m, 40 to 80% by mass of second fibers obtained by crimping natural fibers having a fiber diameter of 10 to 40 ?m, and 10 to 30% by mass of third fibers having a fiber diameter of 5 to 10 ?m. The filter material has low pressure loss a high dust holding amount, and high dust filtration efficiency.

Abstract: A filter element has an upstream-side filter layer and a downstream-side filter layer. The downstream-side filter layer is attached to the upstream-side filter layer. A non-woven fabric made of resin fibers formed by a spinning process constitutes the upstream-side filter layer. The resin fibers have an average diameter within a range of 2.5 ?m and 10 ?m. The non-woven fabric has a weight per unit area within a range of approximately 2.5 g/m2 to 15 g/m2. The downstream-side filter layer has a finer mesh than the mesh of the upstream-side filter layer.

Abstract: There is provided an air filter, which has a long lifetime and permits to capture effectively carbon particles and reduce costs. The air filter has the first filter layer 11 impregnated with oil and the second filter layer 12, which is provided on the downstream side of the first filter layer 11 and serves as a lipophobic layer having an oil-repellent property. The filter material of the first filter layer 11 has a higher density than the filter material of the second filter material 12.

Abstract: There is provided an air filter, which has a long lifetime and permits to capture effectively carbon particles and reduce costs. The air filter has the first filter layer 11 impregnated with oil and the second filter layer 12, which is provided on the downstream side of the first filter layer 11 and serves as a lipophobic layer having an oil-repellent property. The filter material of the first filter layer 11 has a higher density than the filter material of the second filter material 12.

Abstract: The object of the present invention is to provide an air filter where the lifetime of the air filter is long and a carbon dust can be efficiently caught with keeping the cost low. The air filter of the present invention comprises a first filter layer 11 impregnated with oil; an oil repellent layer 11a disposed in the downstream side of the first filter layer 11, having the property of repelling the oil; and a second filter layer 12 disposed in the downstream side of the oil repellent layer 11a, impregnated with no oil. The transfer of the oil to the second filter layer 12 is controlled by the oil repellent layer 11a.