What cooling device did Leonardo da Vinci design with rotating blades to move air?

Leonardo da Vinci designed a mechanical fan with rotating blades to move air.

Leonardo’s notebooks contain studies of devices that use rotary motion to create an airflow. A fan transfers energy from a rotating mechanism to the surrounding air, producing a current that can provide ventilation or cooling. His sketches explored this principle in the context of mechanical engineering rather than electric appliances.

The design should not be described as an electric fan. Electricity was not available in Renaissance Europe, so any operation would have depended on human power, a spring, or another mechanical source. Leonardo’s broader work repeatedly examined how rotary motion could be generated, controlled, and redirected.

A mechanical fan also differs from a windmill. A windmill uses moving air to turn blades and produce mechanical work, while a fan uses mechanical work to move air. Leonardo’s concept belongs to the latter category, making it an early example of powered ventilation thinking.