Method 1: 1. First unscrew the manual nut of the impeller clockwise, and then remove the impeller very carefully; 2. Then dip cotton yarn or soft cloth in a proper amount of kitchen cleaning neutral detergent to soak and clean the ventilator impeller; 3, until the oil is washed clean, and then rinse the residual liquid on each part with clear water; 4. When reassembling the impeller, first inject a few drops of No.20 engine oil or sewing machine oil into the motor shaft;