Shaft buildings will be used as emergency exits. In the metro tunnel there is a shaft, reaching up to the surface every 600 metres, for emergency exit, smoke extraction, pressure equalisation and ventilation. There is an emergency exit stairway with fire compartments in the middle of each shaft. The exits of the vertical shafts are in streets or public parks.
Shaft buildings are technical buildings approximately the size of a small house with a height of around three metres and a surface area of around 100 m2. The surrounding area of a shaft will be landscaped according to a shaft-specific yard plan. The surface material of the shafts in the Ruoholahti–Matinkylä stretch is steel grid plate.