Installing air filters in classrooms has surprisingly large educational benefits (2020)

I wish there was more data on the effects of gasses in the air on people.

We seem to know:

- Elevated CO2 in rooms impairs cognitive performance.

- Elevated CO2 in submarines, at levels far higher than you would see in a normal room does not appear to impact cognitive performance.

- Installing carbon filters (what this study actually looked at) might improve classroom performance.

- People don’t like stuffy rooms.

All this is consistent with multiple hypotheses. It could be that we just don’t know anything about it. Or maybe there is some gas or gasses emitted by people that isn’t CO2 that makes people mildly uncomfortable and have worse cognitive performance.

CO2 is certainly a good proxy for ventilation quality in a space where air is exchanged with outdoors but where the gasses in the air are not otherwise changed. Carbon-filtered classrooms and submarines are not examples of this.

CO2 is a proxy for many other gasses. Cheap CO2 sensors sense volatile organic compounds (VOCs), and use those to estimate CO2.

Many of those gasses do impact cognitive performance. It's not obvious to me why CO2 would, but if CO2 is going up, so is everything else we breathe out. CO2 where I am is somewhere in the ≈400ppm-1000ppm range -- 0.04% or 0.1% -- and it's pretty inert. I'm not sure what harm it does.

If it does to harm, rising CO2 levels should be much more concerning than "just" climate change.

But I suspect it's other gasses.

Rising co2 levels I believe are nowhere near the differential inside vs outside when windows are closed. There’s lots of reason to believe that rising co2 specifically lowers cognitive performance - our brains work on o2 and our body actively works to expel co2 as a waste product - increasing co2 levels means the body has less O2 available and has to work harder on co2 expulsion for survival instead of powering the brain.