What is ID and FD in a boiler?

In boiler systems, Induced Draft (ID) fans and Forced Draft (FD) fans serve opposite but equally vital functions in managing airflow and combustion efficiency.

ID Fans create negative pressure by extracting flue gases from the boiler and directing them toward the chimney. They are located after the boiler and prevent gas backflow by maintaining proper exhaust.

FD Fans generate positive pressure by pushing fresh air into the furnace to support combustion. Positioned in front of the boiler, they ensure a steady and sufficient air supply for efficient fuel burning.