... measured air volume of better quality type of fan is about 40000 cubic meters,but our fan can ... corrosion and air-slake. The material of shutter is PVC,also resist corrision and air-slake. Fan ... the rotation speed of our motor is just 450rpm,so its failure rate is very low,however,the rotation ... s “work”,and he has good temperament,what is important is that he is strong,you needn’t pay too much ...