Fiber waste generated adjacent the knitting section and the yarn feeding members of the machine is conducted by air streams into the lower end of a first duct extending upwardly from the knitting section. The air and therein entrained fiber waste passes from the upper end of the duct and then sequentially through a laterally extending second duct and a vertically extending third duct to a waste collection box. The third duct is made of flexible fabric, vinyl or similar material having therein a multiplicity of small openings that permit lateral passage of air from the duct, while restricting lateral passage of fiber waste from the duct. A funnel-shaped member within the collection box compacts the waste entering the box. The first duct has vertically aligned sections that are telescopically adjustable.