Which component of a fire alarm system utilizes a flexible round plastic paddle or vane?

The component of a fire alarm system that utilizes a flexible round plastic paddle or vane is the water flow switch. This device is designed to detect the flow of water in a sprinkler system. When water begins to flow, the paddle moves with the current, triggering the switch to activate the fire alarm system. This activation ensures that emergency services are alerted to the presence of water flow, signifying that a sprinkler head may have been activated due to a fire.

This mechanism is crucial for early detection and prompt response, as it indicates that a fire suppression system is operational. It is specifically engineered to respond to the detection of the movement of water, which differentiates it from other components like smoke detectors, pull stations, and alarm panels, which serve different functions in the fire alarm system.