A new type of spiral‐flow dropshaft, composed of a vertical circular shaft with tangential inlet and outlet conduits and one or more continuous helicoidal ramps attached to the shaft wall, is described. Experimental results indicate that these helicoidal‐ramp dropshafts are superior to other types of dropshafts both in their energy‐dissipation and air‐handling characteristics. Additionally, the needs for energy‐dissipation and deaeration chambers at the bottoms of these structures are obviated. The friction factors of flows along the channels formed by the helicoidal ramps are somewhat higher than those of equivalent straightchannel flows. Prototype‐installation experience indicates that helicoidal‐ramp dropshafts are significantly cheaper than conventional ones in installations requiring low air discharges from and intensive energy dissipation in the dropshafts.