Air filter medium, air filter pack and air filter unit comprising the same, and method for producing air filter medium

摘要

An air filter medium comprising a porous polytetrafluoroethylene film and an air-permeable support member laminated on at least one surface of said porous film and having a PF1 value exceeding 22, which is calculated according to the following formula: PF1 = Ä-log(Penetration (%)/100)/Pressure loss (mmH2O)Üx100 in which the penetration (%) = 100 - Collection efficiency from a pressure loss (unit: mmH2O) measured when an air is flowed through the air filter medium at a flow velocity of 5.3 cm/sec. and a collection efficiency (unit: %) measured using dioctyl phthalate having a particle size of 0.10 to 0.12 mu m. This air filter medium has a low pressure loss and a high collection efficiency.