Let's talk about airliner cabin air.

I’ve been flying large, pressurized airliners for 38 years. During that time I’ve checked out on a half dozen different types and they all have some things in common regarding the way they handle cabin air.

The first thing is that all the air is tapped from the engine compresser stages. At that point it is extremely hot and guaranteed sterile. It is cooled to a usable temperature and then distributed to the cabin.

In the cabin, the flow of air is mostly from top to bottom. It flows out of ducts above your head next to the skin and flows into return ducts by your feet, also by the skin. From there, it flows to the rear of the airplane under the floor.

At the rear of the plane, in older models it is exhausted overboard. In newer models, about half of it is exhausted and the rest is recirculated after passing through virus-class filters. So, all the air circulating in this way is either sterile to begin with, or has passed through filters that are supposed to be better than any typical face mask.

The one other source of cabin air is from the gasper vents over the seats. These are the small eyeball vents that you can open or close and swivel around if you want. This air is not recirculated. It comes directly from engine packs in its own separate ductwork. It is therefore the most sterile source of air since it is never mixed with recirculated air.

The way the system works, 100 percent of the air in the cabin is changed every two to four minutes, depending on how old the airliner is. Older ones change air faster.

Obviously, sitting close to someone who is coughing or sneezing without a mask is a hazard no matter what. But someone several rows from you is unlikely to give you the virus-at least not in flight. The greater hazard will be during boarding or deplaning.

So, my personal strategy:

-Take a window seat to take advantage of the way cabin air circulates.
-Use the gasper vent to blow sterile air just in front of your face, or to create an air curtain between you and a close neighbor.
-Avoid standing in the aisles during boarding and deplaning.
-Wear a mask as much as possible.

For those of you who will be flying during this time, I hope you find this information helpful.