Engine room air vent shafts + escape tunnel:- (#10 on the layout map)

There were from what I could see 2-3 air ventilation shafts (now blocked off) which connected to the central underground engine room. There were ladders in these cylindrical shafts but they have since been destroyed and thrown down the shaft.
Notice the metal box frame around the openings of these vent shafts, perhaps it had metal louvered sides when it was it was new.

In this general area is also the escape exit tunnel from the underground engine room, as shown in the 1st picture.