A breathing circuit for use with a ventilated patient that includes a heat exchanger for removing water vapor from the breathing gases to prevent condensation within the breathing circuit. The heat exchanger is positioned downstream from the CO.sub.2 absorber and receives the breathing gases from the CO.sub.2 absorber prior to delivery of the breathing gases to the inspiration limb of the patient circuit. The heat exchanger includes a plurality of inflow tubes and outflow tubes that are each open to a sump removably attached to the heat exchanger. The sump collects the water vapor condensed from the breathing gases within the heat exchanger.