Air-conditioning device, in particular for a railway vehicle

The device (10) has a primary circuit (12) in which a refrigerant circulates, and including an evaporator (24) and a secondary circuit (14) in which fluid circulates. The fluid is passed through the evaporator to exchange heat with the refrigerant. The secondary circuit includes a heat exchanger (30) in which the fluid exchanges heat with inside air. A compartment (42) houses the primary circuit. An air treatment zone (44) is formed outside the compartment to communicate with inside air, and houses the heat exchanger. A sealed wall (46) separates the compartment from the treatment zone.