A near-patient humidification system provides vapor to a respiratory breathing circuit. The system includes an expiratory gas conduit and an inspiratory gas conduit. A patient coupling member is provided for coupling the expiratory and inspiratory gas conduits to a patient interface. A vapor injection unit is located at least partially within the housing of the patient coupling member. The vapor injection unit heats a supply of fluid into vapor and injects the vapor into the inspiratory gas passage of the patient coupling member at a vapor injection location for providing moisture to the inspiratory gas flow. A method of simultaneously and independently controlling the temperature and humidity of inspiratory gas in a respiratory breathing circuit is performed by injecting vapor having a temperature determined as a function of measured temperatures and measured humidities of the breathing gas at different locations along the breathing circuit.
