ID Fan stands for Induced Draft and is located between dust collector and chimney. Basically, ID Fan will take the hot flue gases from furnace via dust collector system (dust separation system or fume extraction system) and then it will deliver to the chimney. Induced Draft Fan will handle the flue gases i.e. hot air. Induced Draft Fan will produce the lower pressure than the atmospheric pressure in the system or we may say that ID fan will produce the negative pressure to remove the flue gases from furnace via electrostatic precipitators and to push the flue gases to chimney.