Noun
a duct that provides ventilation (as in mines)
Source: WordNetair-duct
For only $79, our highly trained technicians will do a full air duct cleaning and sanitation to make sure that the air you breathe is free of bacteria. Source: Internet
The officer then stripped down to his pants and t-shirt, climbed in, removed the air duct and found little Kolson eight feet down the vent unharmed, with only a few scratches. Source: Internet
The draft of air from the air duct mixes with the fuel to form a fuel/air mix which is almost gaseous at this time. Source: Internet