An air ventilation fan, also known as an exhaust fan or air extractor, is a device designed to improve air circulation and remove stale or polluted air from an enclosed space. These fans work by creating a flow of air, typically by utilizing electric motors or mechanical mechanisms. 

Air ventilation fans are commonly installed in areas where proper air exchange is essential, such as bathrooms, kitchens, attics, basements, commercial buildings, and industrial settings. The fans pull out the stagnant or contaminated air and expel it to the outside environment, allowing fresh air to enter and maintain better indoor air quality. Ventilation fans can help control humidity levels, remove odors, prevent the buildup of moisture, and reduce the risk of mold and mildew growth.

 They come in various sizes and types, including ceiling-mounted, wall-mounted, or inline fans that can be connected to ventilation ducts. Some ventilation fans may also incorporate additional features like built-in filters or adjustable speed settings. The installation of air ventilation fans promotes a healthier and more comfortable indoor environment by ensuring proper airflow and ventilation.