An improved humidifier which may be used with a nasal cannula for high-flow respiratory gas therapy wherein a sterilized liquid is drawn from a sterilized liquid container by a high-flow driving gas passing adjacent to an aspirator tube orifice through which the sterilized liquid is drawn into contact with the driving gas for fracturing the liquid into a mist which is warmed and delivered to the patient or user, and the driving gas is also passed adjacent a condensate return orifice which draws any condensate formed in the humidified respiratory gas delivery system away from the cannula and back into the system for re-use.