An experimental examination of a novel device for enhancing the gas absorption into an aqueous absorbent flowing down the outer wall of a vertical cylinder was reported. This device utilizes flexible strings tightly wound around the cylinder, taking the form of a multiple helix. The absorbent flows along parallel channels partitioned by the strings, maintaining mutual contact with the surrounding gas for a longer time than it would when it flows down the same cylinder wall in the absence of such strings. Both flow-observation experiments and absorption experiments using water as the absorbent flowing along a single helical channel and carbon dioxide as the gas to be absorbed were carried out. The effectiveness of the helical-flow device for promoting the absorption was recognized at water flow rates high enough to induce an oscillatory flow mode accompanied by periodical liquid-gas interface deformation. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 3109-3118, 2013