A housing for a humidifer is provided which facilitates assembly of the humidifier with the inlet duct positioned either to the left or to the right of the humidifier housing. This assembly is made possible by providing the housing with similar first and second walls and a pair of end walls which extend between the first and second walls. A back defines a first opening and one of the ends defines a second opening midway between the first and second walls so that air can be humidified by passing the air through the housing between the first and second openings. The other of the ends is adapted to receive drive means for driving a humidifier from inside the chamber and one of the ends provides means adapted to receive a water inlet assembly so that the housing can be assembled with one or the other of the first and second walls uppermost depending upon the desired location of the second opening.