What is the difference between ID fan and FD fan?

The difference between ID fan and FD fan

ID fan is basically mentioned here for Induced draft fan and ID fan is always located between dust collector and chimney. ID fan will take the hot flue gases from furnace via dust collector (dust separation system or Fume Extraction system) and will deliver to the chimney. ID fan will handle the flue gases i.e. hot air.

ID fan will produce the pressure lower than the atmospheric pressure in the system or we may say that ID fan will produce the negative pressure in the furnace to remove the flue gases from furnace via electrostatic precipitators and to push the flue gases to the chimney.

Do not get confused about the dust collector system. Dust collector system also designated as fume extraction system or dust separation system. Somewhere we also used to electrostatic precipitators in place of dust collector system for removing dust particle from flue gases for maintaining the clean environment.

FD Fan

FD fan, which is mentioned here for the forced draft fan, is used basically for providing the required quantity of hot air to the furnace for smooth and uniform combustion of fuel. FD fan will produce the positive pressure inside the system i.e. furnace.



  • The inlet to air preheater
  • Handle cold air
  • Less maintenance, consume less power as the density of cold air is less.


  • Locate at foot of the stack
  • Handle hot gas, hence more power is required
  • Cope with corrosive combustion products and fly ash

Share this post