To prevent the accumulation of lint, debris and other contaminants in the needle and dial slots of a circular knitting machine.

A space between a cylinder 14 and a dial 16 is surrounded with a circular air chamber 52, and the flow of pressed air is charged into the chamber 52 to prevent the accumulation of lint, debris and other contaminants in needle and dial slots 18, 36. It is necessary that the air flow only upward escapes from the chamber 52 through a space between the cylinder 14 and the dial 16. In the space, the tint, debris and the other contaminants are blown away with the air flow from the circular knitting machine components (e.g. needle 20, sinker 38) with the air flow. The air flow is thus utilized for preventing the accumulation of the substances in the cylinder 14 and the dial slots 18, 36. The conventional needs for flushing the cylinder slot 18 is reduced or excluded.