In a gas furnace, what is the result of having a clogged flue pipe?

A clogged flue pipe in a gas furnace can indeed lead to possible carbon monoxide buildup. The flue pipe is critical for venting combustion gases, including carbon monoxide, safely out of the home. When this venting pathway is obstructed due to a clog, the harmful gases can’t escape as intended and may enter the living space instead. This poses a significant safety hazard, as carbon monoxide is odorless and colorless, making it difficult to detect without proper alarms.

If the flue pipe is not clear, the furnace may not operate effectively, leading to other issues, such as reduced heat output, but the most immediate and dangerous concern is the risk of carbon monoxide poisoning. Therefore, ensuring that the flue pipe is unobstructed is essential for both the efficiency of the furnace and the safety of the occupants.