The living quarters were protected from gas attacks by means of an air-tight compartment between two armored air-tight doors which constituted their entrance.
The air supply was by means of tubes which passed through the walls beside the armored doors and which connected the ventilation and air purifying unit (located in the chamber of the living quarters) to the outside and to the other chambers.
The longitudinal grooves along the walls were created during the pouring
of the concrete. They were intended for the passage of cables, tubes etc.,
but often were left empty. Where the installation of an air tight door
was planned, a channel surrounding the opening was also left for the metal
door frame. This channel was then filled with cement in order to hold the
frame in place. At the same time the longitudinal grooves beside the door (along
with any cables or tubes) were also filled with cement in order to
prevent any air passage.
The air tight closure of the doors was assured by
gaskets made of asbestos, since rubber was scarce because of the sanctions
applied against Italy during the fascist period.
