The Collaborative International Dictionary of English v.0.48:

Air shaft \Air" shaft`\
   A passage, usually vertical, for admitting fresh air into a
   mine or a tunnel.
   [1913 Webster]

WordNet (r) 3.0 (2006):

air shaft
    n 1: a shaft for ventilation [syn: air shaft, air well]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "air shaft":
   air duct, air hole, air passage, air tube, airway, blowhole,
   breathing hole, louver, louverwork, naris, nostril, shaft,
   spilehole, spiracle, touchhole, transom, vent, ventage, venthole,
   ventiduct, ventilating shaft, ventilator, wind tunnel