Hmmm. Boarding a flight for an urgent work trip. Thought I might look at the amount of recycled air inside the plane. Steadily increased from 600ppm to 1300ppm as the door closed. Being on the ground is the worst air.... supposedly. Let’s see.
Caveat to all of this. BOS-LAX. I am fortunate that I am sitting in business class without a neighbor (my requirement of flying during a pandemic). But I am also in a little box of my own. Little encased cabin which rises above my head height when seated.
I was interested in the recycled fraction. The air coming straight from the nozzle is a mix of outside air and direct from HEPA filter air. I saw 1200-1256 at 1 minute intervals over 5 minutes (my arm got tired after that).
Time out from the science.... this is not your ordinary plane food! Damn! Yes, that is a lobster roll!
The next phase : car service from LAX to hotel. Barriers in car, two windows open, air on flow through. Still higher than I would like.