Titanic Photo: 

This photograph shows a large ventilation shaft designed to feed fresh air into the furnaces of the No. 5 boiler room on Titanic. Originally, a cowl head (chimney covering) was placed over the shaft to prevent rain from seeping in, but the cover has since corroded and vanished. Vent shafts are usually empty, but this vent shaft held access ladders and platforms to permit inspection and maintenance of the shaft, steam pipes and electrical cables.