An image forming apparatus includes first and second rollers forming an image fixing nip, the second roller being disposed below the first roller; a casing accommodating the first and second rollers and having a sheet introduction opening and a sheet discharge opening; a suppression portion provided at a position, away by not less than 0.5 mm and not more than 3.5 mm, from a surface of the first roller in a space extending from the sheet introduction opening to the sheet discharge opening and configured to suppress scattering of particles of predetermined particle sizes resulting from the parting material adjacent the sheet introduction opening; and a substantially closed chamber provided above the casing and having an entrance for permitting entering of the particles guided to the outside of the casing by the suppression portion to stagnate the particles.