• One reason for this is that the sparks can enter the house through a fireplace opening serving a woodstove elsewhere along the line. Multiple connections can cause flue gases and sparks to pass from one flue opening to another, and ignite unburned gases in the flue . Both a fireplace opening and an oil furnace’s barometric damper will furnish large quantities of air to their flues. In the event of a chimney fire, this will hamper any attempts to extinguish the fire by restricting airflow to the flue.

• Using a wood-burning stove on a flue serving an oil furnace may also reduce the efficiency of the oil furnace, due to the change in draft characteristics of the flue. Multiple connections sometimes result in insufficient draft and lower efficiency.

• Always refer to your local building and fire code to ensure that heating equipment and systems are properly installed, maintained and operated.