centrigugal shutter style ventilator 

centrifugal fan  Products Features:

1)Shutter: with a centrifugal system which can ensure the shutter open and close automatically, and makes it dustproff, waterproff.

2)Motor: the high efficient and energy-saving motor eith protection grade:IP55,insulation class:F

3)Belt:automatic tensioner to prevent the belt loosing and froping off.