Housing with a cover with gasket and locking element for a heating, ventilation and /or air conditioning installation for a passenger compartment

The box has a cover comprising two passages adapted with openings that are disposed against a front end side of a heat exchanger and integrated to a front end wall. Two flange rings (39, 40) are assembled and arranged for limiting air output through an opening in the front end wall and passages. The cover includes an external side equipped with two parts surrounding the passages.