Abstract: An air filter unit has a pleated filter medium with a zigzag shape in which a fibrous filter medium has been folded multiple times. The coefficients of linear expansion of the space-supporting members provided in each of the multiple folded spaces of the pleated filter medium are equal to or greater than the coefficient of linear expansion of the metal filter frame of the filter unit. The linear expansion coefficients of first space-supporting members are smaller than the linear expansion coefficient of a second space-supporting member. The first space-supporting members are provided in side portion regions including both side portions positioned at outermost sides of the pleated filter medium in a second direction perpendicular to the first direction. The second space-supporting member is provided in a central portion region sandwiched between the side portion regions.

Abstract: An air filter unit has a pleated filter medium with a zigzag shape in which a fibrous filter medium has been folded multiple times. The coefficients of linear expansion of the space-supporting members provided in each of the multiple folded spaces of the pleated filter medium are equal to or greater than the coefficient of linear expansion of the metal filter frame of the filter unit. The linear expansion coefficients of first space-supporting members are smaller than the linear expansion coefficient of a second space-supporting member. The first space-supporting members are provided in side portion regions including both side portions positioned at outermost sides of the pleated filter medium in a second direction perpendicular to the first direction. The second space-supporting member is provided in a central portion region sandwiched between the side portion regions.