Ventilation balls, ball bearing systems (ball bearings are easier to spin than Bruce systems) or ventilation fans. That does not require electricity. The rotating ball system is caused by the use of natural wind that allows the air to flow all the time. make the air not stuffy save electricity Used for ventilation from inside the building to the outside of the building. Suitable for enclosed backyard kitchens. no ventilation vents
Installed and ventilated, not stuffy, not stuffy Installed and do not require maintenance throughout the lifetime. Suitable for houses, warehouses, farms, installation area 20 sq.m./location, can be installed on all types of roofs.