Even better is to wear a mask (not to prevent virus from coming in that's silly air gets around it) but to keep your nasal passages moist during a high altitude flight. Japanese have known this for years and why they wear masks so much.
I started wearing N95s on flights since KF94 ear loop masks would hurt my ears after a few hours. Inadvertently realized during fit-testing that the KF94s let so much air around the edges that they were much less effective than I had assumed, so I basically just use my N95 when needed indoors anywhere. Also found that other 3M mask models didn't fit my face as effectively (failed the test almost immediately).
Highly recommended to go with fit-tested N95s (if not already using something even better like a respirator).
Edit: I should mention I've flown SF to Toronto a few times since the pandemic started and air quality on planes is quite terrible despite what airlines say. Lowest CO2 concentration around 1800 ppm, and highest I've seen has been 3000+ ppm (during boarding). (420ppm outdoor average at sea level, and anything about 1000ppm I'd wear a mask indoors.)
I am also curious how you connect CO2 levels to pathogen levels. Would a carbon filtration system adjust the CO2 levels at the same rate as pathogens?
they aren’t directly correlated, it’s just a proxy. ventilation reduces both.
As sneak also replied, it's just a proxy: higher CO2 correlates to higher chance of breathing in pathogens, but doesn't take into consideration filtration.
It’s worth noting in this context that masks have been shown to protect the wearer, not just to prevent the wearer transmitting viruses. See e.g. https://www.cdc.gov/mmwr/volumes/71/wr/mm7106e1.htm
That obviously depends on how you define a "mask", a "medical mask" has a very different efficacy from an N95.[1]
[1]: https://www.mayoclinic.org/diseases-conditions/coronavirus/i...
Given all the other discomforts of flying, wearing a respirator is a minor problem. Passengers are not likely to have long, emotional conversations during a flight where a mask might be uncomfortable or inhibit communication. But there is the food/drink issue, if someone considers those to be important.
If only we had better air systems to go with these $1,000 tickets , but that's demanding a lot from the makers of 737max and such :p
My less empirical info is that airflow in a plane mostly goes from being input above your head, and exhausted from the pressurized cabin at your feet, meaning you have less exposure to anyone not in your row.
Remember that aircraft pressurization systems were designed to be smoked in, other than the newest designs. They needed enough airflow to not totally choke out passengers on a cross country or cross atlantic trip.
I'm not saying this is the case necessarily for planes, but I'm just trying to provide context for how proxy measures of air quality may not tell the full story.
Most systems lead to a dry throat due to bad filter designs and improper humidity regulation which is a shame.
Thus, wearing a face mask will not effectively keep your nasal passages moist during a high altitude flight.