Filter medium

A multilayered filter medium whose air permeability is at least 500 l/m2sec and which has a least three concrete layers, wherein

• I) the first layer is a melt binder-solidified textile fabric whose fibres have a titre in the range of 1 to 2 dtex,
• II) the second layer is a melt binder-solidified textile fabric whose fibres have a titre in the range of 2 to 4 dtex,
• III) the third layer is a melt binder-solidified textile fabric whose fibres have a titre in the range of 4 to 12 dtex,
• IV) the portion of the first layer of the multilayered filter medium is 20 to 60% by weight, the portion of the second layer of the multilayered filter medium is 10 to 40% by weight and the portion of the third layer of the multilayered filter medium is 10 to 40% by weight,
• V) the melt binder portion in the layers in accordance with to I) to III) amounts to 5 to 40% by weight in total,
• VI) the weight per unit area of the layers in accordance with I) to III) amounts to 50 to 400 g/m2 in total and
• VII) the filter medium, when charged with 5 mg/cm3 SAE dust of the class “fine”, exhibits a pressure increase of no more than 100 Pa.