“A vortex ring generator humidifies the air in passengers’ breathing zones, thereby increasing comfort levels without any material increase in the overall relative humidity in the cabin,” says Thomas Kirmayr, group manager at Fraunhofer IBP. The basic principle is that a generator produces small vortex rings of humid air – rather like the rings sometimes expelled by smokers. The vortex effect keeps the rings stable over a certain distance while preventing them from mixing to any significant extent with the surrounding air. The researchers have designed the generator so that the vortex rings make contact with the passengers’ upper torso; body heat then causes them to rise towards the nose and mouth. Since the chest area is covered by clothing, it is less sensitive than the face would be to the light airflow. The researchers’ goal is to increase air humidity in the breathing zone by up to 15 percent to reach a level of around 30 percent. This can be done by conditioning a minimal amount of air directed in the form of vortex rings exactly where it is needed.