So what is the definition of the word flue? The chimney Safety Institute of America defines this word as, “The passage in a chimney for conveying flue gases to the outside atmosphere.”
And Webster’s Dictionary defines this word as, “A channel or pipe in a chimney for carrying flame and smoke to the outer air.”
The inside of your chimney may contain one or more flues. It depends upon the number of fireplaces or gas appliances are in the home.