Abstract: A room humidifier in combination with a source of potable water and a source of heated fluidic material, such as a room hot water radiator, room steam radiator, room baseboard convector, remote steam boiler or remote hot water boiler. Potable water from its source is supplied to cover a heat exchanger in the humidifier to a desired level. Such potable water is heated by the heated fluidic material flowing through the heat exchanger, causing the formation of water vapor which collects within the humidifier. The desired relative humidity in the room is attained and maintained by control means which causes the flow of the heated fluidic material through the heat exchanger to form such water vapor and the control means causes a fan to operate to draw room air through the humidifier to render such room air moisture-laden and to blow such moisture-laden air into the room.