Baffling is a type of obstruction designed to deflect and regulate the speed of flue gases. They are especially necessary for round boilers and furnaces constructed so that the flue passes are almost direct from the fire box. Furthermore, boilers designed for burning coal are usually provided with relatively large flue passages, which are not normally suited to the higher flue gas velocities, encountered in oil firing.

Baffling will, in most cases, help to partly overcome the inefficient operation resulting from the usual excessively high stack gas temperatures. In such instances it is advisable to experiment with various methods of baffling. (Any baffling of the flue passes of a nature, which prevents efficient operation of the burner, should not be done.

Another form of baffling is a corbel or step out arrangement of the brick work of the rear wall, forming a target wall which the flame strikes and is curled back to prevent short circuiting.