Figure 2.

The lung model consists of a box (a) in which the temperature is maintained at 36.0°C, a one-way valve (b), an elastic balloon (c) and a water bath (d). During the inspiratory phase the air passes from the ventilator (e) through the humidifier (f) via the one way-valve to the balloon. During the expiratory phase the air passes from the balloon and bubbles through the water-bath in order to reach 100% humidity at 35.5°C by the time it leaves the lung model. The arrows indicate the direction of the airflow.