Abstract: A dust-proof fabric having an excellent dust-collecting efficiency and dust-preventing property including a plurality of filament yarns having a thickness of 20 to 400 denier and consisting of a plurality of individual filaments having a denier of 3.5 or less. The fabric has a number of pores formed therein and exhibits an air permeability of 0.3 to 10 ml/cm.sup.2 /sec. In the fabric, the proportion of the integrated volume of pores having a size of 43 .mu.m or more to the entire integrated volume of all the pores in the fabric is 40% or less.

Abstract: A false twist-crimped polyester yarn having a density (d) of 1.3800.ltoreq.d.ltoreq.1.3970 (g/cm.sup.3) and total percentage crimp (TC) of TC 30% is produced by false twisting a polyester multi-filament having a birefringence (.DELTA.n) of 0.030.ltoreq..DELTA.n.ltoreq.0.145 while heat setting the filament in the twisted state at 160.degree. to 210.degree. at a draft (dr) which satisfies the following equation:-150(.DELTA.n) + 17.ltoreq.dr.ltoreq.0.9 .times. 10.sup.4 (.DELTA.n.sup.2)-29 .times. 10.sup.2 (.DELTA.n)+248.