The collapsible single and double-blade rotary paddles offer a unique solution to address safety concerns and avoid OSHA violations by preventing personnel from entering bins. The paddle collapses to fit through a standard 1-1/4” or 1-1/2” coupling, removing the need to climb into the bin to install the device. The two-vane design is best for light to medium weight materials such as feeds, seeds, grains, or materials where more surface area is needed to apply resistance to the paddles. The single-vane design is ideal for heavy materials that need minimal contact to activate an alert. The collapsible paddle is ideal for concrete silos that have thick walls or when a rotary is used to replace a capacitance probe or vibrating rod.