Centrifugal shutter system exhaust fan 1.patented designed centrifugal system which can open and close automaticlly ,ensuring the shutter opens 90 degree under all the condition. And uncontrollable air can prevent from going into the birdhouse when the shutter works. 2.Mirror designed and injection moulding Stainless steel balde,with big air volume,never distortion and broken 3.experiment of homeostasis make the blade work smoothly,nearly no noise and steadily output of air 4.centrifugal shutter system made of high quality engineering nylon ,high strength and long service life 5.high efficient and energy-saving motor with ccc certificate ,protection class:IP55,insulation class:F grade Specifications: Model specifications Blade mm Blade rotational speed rpm Motor rotational speed rpm Air flow m3/h Total pressure Noise decibels Import power Rated voltage High mm Width mm Thick mm AM-1000(43¡±) 900 610 1400 >30000 70 ¡Ü70 750 >380 1000 1000 400 AM-1380£¨54¡¨£© 1250 439 1400 44000 56 ¡Ü70 1100 380 1380 1380 400. Size :1380mmx1380mmx450mm Weight:91kg Packing:standard exporting paper carton.