Abstract: A convertible function water vapor generating device is provided for use with medical oxygen delivery systems for creating a nebulizing mist suspended in the oxygen flow and for creating a bubble humidified oxygen flow. An oxygen handling component may be connected to a refillable and/or disposable water container which may be prefilled and which preferably has a passageway for directly accessing the bottom of the water supply held therein. A heater for heating water accessed may reside as part of the handling component which also may contain a nebulization nozzle and a nebulizer-humidifier function control.