An enclosed passageway in which to direct air or other gaseous current along.
A pipe or duct that carries gaseous combustion products away from the point of combustion (such as a furnace).
In an organ flue pipe, the opening between the lower lip and the languet.
Any small aperture or vent for air or other fluid.
A pore or opening used (especially by arthropods and some fish) for respiration.
The blowhole of a whale, dolphin or other similar species.