A rotary ventilator is a passive ventilation device, a non-electric alternative to mechanical ventilation, these vents use the natural force of wind and air pressure to spin and vent out stale air. They do it with a series of specially shaped vanes that catch the wind and provide rotary motion. This pulls out hot, humid air. Rotary vents provide a low-cost ventilation alternative in areas where wind speeds of at least 5 mph are typical so perfect for caravans while on the open road under a baking sun. A well-designed rotary ventilator takes advantage of the wind to create a positive flow through the throat of the ventilator. Passive vents work for free and in almost all instances are silent.
Also known as a whirly bird.
