Abstract: This invention concerns a steam generator (100) intended to humidify the air in an enclosed space or the air treated in an air conditioning system, particularly an air conditioning system aboard an aircraft, said steam generator (100) comprising at least one tank (110) intended to contain a water-based fluid (E), said or each tank (110) being connected to a heat exchanger (210) intended to convert the fluid (E) into steam. The steam generator (100) is remarkable in that the heat source connected to the heat exchanger (210) is a thermochemical reactor (230).