[jonpurdy]

On this topic, I recently got officially fit-tested for N95 masks (specifically 3M 9210+). They put a cover over your head and spray in a bitter substance; if you taste it, the mask fit fails. (You can also do this test at home if you have the supplies.)

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.)

[MobileVet]

How are you testing air quality on the plane?

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?

[sneak]

co2 levels are an inverse proxy for incoming fresh air fraction. this is of course inversely correlated with pathogen concentration (presuming that fresh incoming air from outside is relatively pathogen-free).

they aren’t directly correlated, it’s just a proxy. ventilation reduces both.

[MobileVet]

Makes sense, thanks for the reply

[jonpurdy]

aranet4 CO2 monitor that I bring with me. 2xAA batteries allow it to go for a year or more, and I can pull the readings via Bluetooth to my phone to look at historical data.

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.