Ventilation shaft

The Tenth Doctor found a ventilation shaft in Area 51. Observing that "there's always a ventilation shaft", he claimed that there was always a way out of them, "apart from in Star Wars, of course." (TV: Dreamland)

Jack Harkness climbed through two miles of ventilation shafts aboard the Crucible. (TV: Journey's End)

Rose Tyler referred to the maintenance tunnels in Sanctuary Base 6 as ventilation shafts. John Jefferson, while appreciating the reference, explained that there was no ventilation and no air, having been designed for machines and not life forms. (TV: The Satan Pit)

Aboard the Game Station, the Daleks travelled in hover position between floors using the ventilation shafts. (TV: The Parting of the Ways)

When the Masters of Dorada conquered Dorada and enslaved the native Doradans to work in underground factories, some of them took refuge in the factories' ventilation shafts; those who were born there were immune to the Masters' control. (PROSE: The Dream Masters)

An unspecified incarnation of the Doctor had no plans in his Five Hundred Year Diary one day, and so decided to study ventilation shafts. (PROSE: Doctor Who and the Krikkitmen)

Behind the scenes
In NOTVALID: The Curse of Fatal Death, the Ninth Doctor describes Emma as "a girl more exciting than an escape up a ventilation shaft."