Roof turbo ventilator:purify indoor air,high fuction of exhaust,environmental protection, cost ... by the difference in temperature. The hot air rises, cold air falls, which make the ventilator rotate, and ... As a result, indoor temperature cools naturally, fresh air exchanges. This product is widely used in facories, ... even in breeze.In order to get a high fuction of ventilation, we used ame-retardant ...