PURPOSE: To enhance heat exchange efficiency by providing a substantially rectangular frame having a plurality of horizontal rods and two vertical rods, and triangular projection plates disposed between adjacent horizontal rods so that an introduced air flow can be formed into wave-shape or snaking shape.

CONSTITUTION: This filler comprises a rectangular frame 1 having several rods 1a extending horizontally, and two rods 1b extending vertically, and projection plates 2,... disposed between adjacent horizontal rods 1a. Each projection plate 2 has upper and lower edges 21, 22 boded to adjacent horizontal rods 1a. Upper edge 21 of the projection plate 2 has the same length as the lower edge 22 but the intermediate part 25 is shorter than the upper and lower edges 21, 22. Consequently, a row of rhombic openings 26 are formed between adjacent projection plates 2 such that air can flow through the rhombic openings 26. Since the projection plates 2 are arranged alternately to form a zigzag row.