A humidification device for a respiratory breathing circuit, comprising: an induction heater assembly configured to inject steam into a breathing circuit gas line of the respiratory breathing circuit, the assembly comprising: a housing having a proximal end and a distal end, the housing defining a housing lumen extending from the proximal end to the distal end; an induction element located around at least a portion of the housing lumen; and a power assembly in the housing for connection to a power source; a cannula (202, 302) having a proximal end (206, 316) and a distal end (208, 318), the cannula (202, 302) being disposed within the housing lumen and surrounded by the induction element, the cannula (202, 302) being configured to receive a flow of water; and a heating element (212, 312) located inside the cannula (202, 302), the heating element (212, 312) being at least partially surrounded by the induction element, wherein the induction element is configured to be excited by electrical current supplied from the power assembly, to generate an oscillating magnetic field to create eddy currents in the heating element (212 312) to heat the heating element (212, 312), and thereby heat the flow of water in the cannula (202, 302) flowing past the heating element (212, 312), to thereby vaporize the water into steam which exits the induction heater assembly and housing to be injected into the breathing circuit gas line. an induction heater assembly configured to inject steam into a breathing circuit gas line of the respiratory breathing circuit, the assembly comprising: a housing having a proximal end and a distal end, the housing defining a housing lumen extending from the proximal end to the distal end; an induction element located around at least a portion of the housing lumen; and a power assembly in the housing for connection to a power source; a cannula (202, 302) having a proximal end (206, 316) and a distal end (208, 318), the cannula (202, 302) being disposed within the housing lumen and surrounded by the induction element, the cannula (202, 302) being configured to receive a flow of water; and a heating element (212, 312) located inside the cannula (202, 302), the heating element (212, 312) being at least partially surrounded by the induction element, a housing having a proximal end and a distal end, the housing defining a housing lumen extending from the proximal end to the distal end; an induction element located around at least a portion of the housing lumen; and a power assembly in the housing for connection to a power source; a cannula (202, 302) having a proximal end (206, 316) and a distal end (208, 318), the cannula (202, 302) being disposed within the housing lumen and surrounded by the induction element, the cannula (202, 302) being configured to receive a flow of water; and a heating element (212, 312) located inside the cannula (202, 302), the heating element (212, 312) being at least partially surrounded by the induction element, wherein the induction element is configured to be excited by electrical current supplied from the power assembly, to generate an oscillating magnetic field to create eddy currents in the heating element (212 312) to heat the heating element (212, 312), and thereby heat the flow of water in the cannula (202, 302) flowing past the heating element (212, 312), to thereby vaporize the water into steam which exits the induction heater assembly and housing to be injected into the breathing circuit gas line.