a building's air/heating/ventilation 'ducts'
the bile 'duct'
tear 'ducts'
(..) That's you. In five minutes, a poisoned gas pellet containing propane lithium compound... ...willbe released through thousands of air ducts in this city... ...effectively annihilating half the population of Metropolis. I was a reporter before most of my friends were copy boys. (..)1978 Superman