The air in airliner cabins is typically kept very dry. It has to be, in order to stop condensation from accumulating within the plane. Unfortunately, this also dries out passengers' mucus membranes, causing discomfort. Germany's Fraunhofer Institute for Building Physics is creating what may be a solution, however, in the form of personal rings of moist air for each passenger.
The idea is that every seat on an aircraft would have a device built into the back, known as a vortex ring generator.
In the same way that smokers can blow rings of smoke, this generator would puff rings of humidified air at the passenger sitting behind it. Given that it might be off-putting to be getting constantly puffed in the face, though, these rings would instead be aimed at the chest, hitting the passenger's shirt – their body heat would then cause the moisture to rise to their nose.
In this manner, the humidity of the air in each passenger's "breathing zone" could be boosted by up to 15 percent, while the overall humidity of the air throughout the cabin would only be raised slightly. Additionally, it's possible that some of the water used for humidifying the vortex rings could be drawn from the cabin air itself. The moisture would then simply be getting concentrated and redirected to where it's needed most, as opposed to being added to the environment.
The system has already been tested on a dummy equipped with a moisture-measuring "nose," and plans are in place to ultimately test it on human volunteers. Given how long it can take to get regulatory approval for technologies intended for use in aircraft, however, it may be a while before it comes into common use.