In the corridors of the dormitory cells, they proceed to heating the air-box located between the dust keep lining and the coffered ceiling of the cells.
The air circulated by thermal convection in the air-box opening while being heated by two fireplaces in own cameras (calefactórios), of which, one does still exist. When cooled, the air flew down to the corridors of the cells being again reheated in the calefactories.