Dust or white ash generated during fiber or fabric processing is a constant problem for manufacturers. This study examines dust formation, its characterization, and prevention during the treatment of PET fabrics. Dust is collected from three stages of PET fabric processing for detailed characterization—fiber texturing, fabric weight reduction, and fabric dyeing. IR and NMR are used to characterize the chemical structure, GPC to determine the molecular weight, and DSC to measure Tm. Accordingly, the main ingredient of the dust from fiber texturing is identified as PET polymer, whereas the dust from weight reduction is primarily terephthalic acid, and that from fabric dyeing is mainly PET cyclic trimer. Furthermore, sedimentation experiments and SEM observations indicate that an alkaline- dye process, pH 9 to 10, helps to create uncontaminated dyeing conditions, where the migrated PET cyclic trimer partially dissolves in the aqueous solution and thus reduces deposits on the surface of PET fabrics. Our results further demonstrate that HOY causes the highest oligomer migration, followed by DTY, and then POY.