Methods: 1. The partition in the middle of the exhaust duct is not straight or open, or the exhaust duct is blocked, which will cause the range hood not to smoke. 2. Reversion or damage of the wind wheel of the range hood will cause the range hood not to smoke. 3. The blockage of the oil fume pipe will also cause the range hood to wash the smoke. 4. The damage of the capacitor in the range hood will lead to the reverse rotation of the range hood, and the reverse rotation of the range hood will also lead to the range hood not smoking.