Abstract: A filter pleat pack includes an air filter medium including: a first porous fluorine resin membrane; and a first air-permeable supporting layer. The first air-permeable supporting layer is placed on a downstream side in a direction of an air flow that passes through the filter medium with respect to the first porous fluorine resin membrane, and includes a ventilation inhibiting portion in at least one end portion in a width direction, the ventilation inhibiting portion extending along the at least one end portion, the ventilation inhibiting portion inhibiting ventilation in the width direction through the first air-permeable supporting layer. The ventilation inhibiting portion is in contact with the first porous fluorine resin membrane. This filter pleat pack is suitable for reducing a decrease in the collection efficiency of an air filter unit even when a gap between a lateral surface of the pleat pack and a frame is sealed.

Abstract: An air filter medium includes a collection layer, an air-permeable adhesive layer, and a porous fluorine resin membrane in this order from upstream to downstream of the filter medium. An initial pressure drop of the filter medium at a permeate flow rate of 5.3 cm/sec is 250 Pa or less. When a test is performed in which polydisperse polyalphaolefin particles having a peak in number in a particle size range of 0.1 to 0.2 ?m are allowed to pass through the filter medium at a concentration of 0.2 to 0.5 g/m3 and a linear velocity of 5.3 cm/sec, the holding amount is 43.0 g/m2 or more from a moment when the holding amount reaches 20 g/m2 to when a moment the pressure drop reaches PD1+120 Pa, where PD1 is the pressure drop of the filter medium at the moment when the holding amount reaches 20 g/m2.

Abstract: A provided air filter medium is an air filter medium including a porous fluorine resin membrane, the air filter medium further including: a glass filter medium layer. The glass filter medium layer and the porous fluorine resin membrane are placed in this order from upstream to downstream of the air filter medium configured to allow an air flow to pass through the air filter medium. At a surface of the glass filter medium layer on an upstream side in a direction of the air flow, a carbon-to-silicon ratio (C/Si) evaluated by X-ray fluorescent analysis is 0.020 or more. This air filter medium is suitable for reducing a pressure drop increase even in an environment including liquid particles such as oil mist.

Abstract: An air filter medium includes a porous fluorine resin membrane, and further includes, a collection layer, an air-permeable adhesive layer, and an air-permeable supporting layer. The collection layer, the air-permeable adhesive layer, the air-permeable supporting layer, and the porous fluorine resin membrane are placed in this order from upstream to downstream of the air filter medium configured to allow an air flow to pass through the air filter medium. The collection layer is formed of a fibrous material having an average fiber diameter of 5 µm or less. The air-permeable adhesive layer has a grammage of 5.5 g/m2 or more. The air-permeable supporting layer is formed of a fibrous material having an average fiber diameter of more than 5 µm. This air filter medium is suitable for reducing a pressure drop increase even in an environment including liquid particles such as oil mist.