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Comment by jonpurdy | Hacker News Reader

I used to think this especially since airlines touted how good the air filtration was when COVID hit.

It's actually quite poor and significantly worse than most indoor spaces I've entered (most spaces aren't great at around 800-1600ppm). On planes I've measured※ very high CO2 levels (1800-4000ppm), with the worst air during boarding and deplaning. This matches the findings of others (both amateur and professional researchers).

※ - using Aranet4

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Are CO2 levels a useful way to measure filtration?

Are we expecting almost all the clean air to be from outside, minimal amounts from recirculation?

Apologies, I specified "filtration" but meant "quality", which I would define as filtration + fresh air intake.

I'd have expected a better mix (more fresh air) since even with filtration removing many particulates and viruses, high CO2 levels still cause worse cognitive performance.

It's hard to get lots of fresh air into a pressurized plane, so I'm willing to have a good bit of leeway on that front. And airflow patterns are important; a lot of fresh air running from front to back would likely do more harm than good.

How does an N95 help with CO2 levels?

I would wager it's not a matter of helping filter out CO2, but rather CO2 is one way to assess how effective the air management is on a plane.

I love how the recent availability of cheap PPM and CO2 sensors spawned a whole new subculture of air quality paranoia.

Based on Veritasium's recent video, given the cabins are pressurized by bleeding air off of the jet engine might not be too surprising about CO2 or particulates. However the cabin air is also exceptionally dry.

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