What is the cause of poor combustion during the combustion process of the burner?

What is the cause of poor combustion during the combustion process of the burner?

(1) It may be that the damper is too small;

(2) If the burner is used for a long time, especially if there is often a lot of dust in the furnace room, the dirt accumulated in the combustion head may cause poor combustion;

(3) Maybe the diameter of the exhaust pipe is too small or the exhaust channel is blocked;

(4) It may also be that the size of the furnace is too small.