If you're anything like me on an airplane, you're constantly fiddling with the air vent above your seat during the flight. Sometimes it's a pain to get the airflow just right, and even after you do, why would you want even more recycled air blowing down on you? This is to say nothing of folks who get cold very quickly.
That vent, however, is more than just a delivery system for air. It can create a barrier around you to ward off germs during your flight.
You read that correctly. It turns out that a flow of air positioned at just the right spot with the right speed will force nasty air particles away from you and onto the ground.
How airplane air circulates
To understand how this works, and why that air from the vent isn't going to make you sick, it helps to consider how air circulates inside an airplane.
The first thing to know is that the air you're breathing isn't recycled throughout the entire plane. You're only sharing air with the passengers in your particular area, about three to seven rows. (So rest easy if there's a person coughing 10 rows away.) Each section has vents that allow air to exit the cabin and then mix with fresh air from outside, which is gathered by the plane's engines.
HEPA filters then do their job of removing around 99.7 percent of the harmful particles and bacteria from the combined air, which is then released into the cabin. Aaaahhh.
This process, according to Travel+Leisure, occurs 15 to 30 times over the course of an hour, depending on the plane. To put that in perspective, your office building air is refreshed around 12 times an hour. (I'm sure your building does it way more often, though. Don't worry.)
So how does that finicky little nozzle keep germs away from you?
Airborne viruses — think measles, tuberculosis and the common cold — can linger in the air for certain lengths of times before falling to the ground. While they're in the air, they're easy to breathe into your body, and since the air in planes tends to be drier, the mucous membrane that we rely on to trap and stop germs from entering the body become drier and less effective.
The air flow of the vent creates a wall of turbulent air in front of you that not only blocks the particles from reaching you but also forces the particles to the ground more quickly. The result is that there are fewer germs to breathe in, and you're helping those in your ventilation section, too, by driving the germs to the floor.
Dr. Mark Gendreau, vice chair of emergency medicine at Lahey Medical Center in Peabody, Massachusetts, and an expert on infectious diseases associated with air travel, has been touting this little trick for a while now. Speaking to NPR in 2014, he said, "Set your ventilation at low or medium. Then position it so you can draw an imaginary line of current right in front of your head. I put my hands on my lap so I can feel the current — so I know it's properly positioned."
With the airborne germs out of the way, you can focus on relaxing (at least a little) during your flight.