1.High entire pressure 2.Big wind,low noise 3.Low ... open and close, windproof, rainproof and dustproof.5Newly punch forming fan blade, reasonable angel and reach the max. air flow, ... quality test process: noise test, vibration test .concentric performance test, fan blade turning speed test, input air teat and vehicle efficiency ... Adopt rivit which is use to plane,fastness never looseness. Exhaust Fan