air shaft

from The Century Dictionary.

• noun Same as air-pit.
• noun Any ventilating shaft.

from the GNU version of the Collaborative International Dictionary of English.

• A passage, usually vertical, for admitting fresh air into a mine or a tunnel.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a vertical (or near vertical) shaft that supplies ventilation to a tunnel or other underground facility

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a shaft for ventilation