A humidification device for a respiratory breathing circuit comprises an induction heater assembly to inject steam into a breathing circuit gas line. The assembly comprises a housing defining a housing lumen. An induction element is located around the housing lumen. A cannula is disposed within the housing lumen and surrounded by the induction element, the cannula being configured to receive a flow of water. A heating element is located inside the cannula, the heating element being at least partially surrounded by the induction element. The induction element is excited by electrical current to generate an oscillating magnetic field to create eddy currents in the heating element to heat the heating element, and thereby heat the flow of water in the cannula flowing past the heating element, to thereby vaporize the water into steam which exits the induction heater assembly and housing to be injected into the breathing circuit gas line.
