A gas humidifier provides a continuous flow of gas through two stages of bubbling with an intermediate heating stage. Gas is introduced into an enclosure containing a quantity of bulk water by pumping the gas into a gas entry pipe or tube. The gas exits the gas entry pipe to bubble up through a bubbling evaporator. At the water surface of the bubbling evaporator, a heating element heats the gas-vapor mixture. The heated gas-vapor mixture then bubbles up through the bulk water, and the temperature of the bulk water determines the thermal cycles of the heating element. The gas-vapor mixture bubbles up through the bulk water, reaching saturation at the dew point. The saturated gas is then directed from the humidifier for use.