Air duct and Flue pipe

Air duct noun - A duct that provides ventilation (as in mines).

Flue pipe and air duct are semantically related. In some cases you can use "Flue pipe" instead a noun phrase "Air duct".

Flue pipe noun - Organ pipe whose tone is produced by air passing across the sharp edge of a fissure or lip.

Air duct and flue pipe are semantically related. You can use "Air duct" instead a noun phrase "Flue pipe".