CO2 and cognitive performance

December 20, 2024

Since a few years I’ve been working a lot from home. During these work-from-home days, I noticed something troubling: after a few hours, I often felt sluggish and sleepy. This pattern seemed to be particularly noticeable during hot summer days or cold winter months.

I suspected air quality might be the culprit, so I did a bit of research and bought a Aranet4 home air quality sensor.

Aranet4 measures some bad air quality in my office

In the mornings, before I start working, I fully ventilate my workspace until the CO₂ level drops to around ~600 ppm. But once I close the door and window to start working, the CO₂ level rises by about 700 ppm per hour! This means that after just one hour, I’m already operating at 1000~1500 ppm — a range that significantly hampers my cognitive abilities.

When I’m deeply focused and lose track of time, the situation only worsens. I can feel my energy draining, my mind becoming foggy, and my productivity taking a nosedive.

To put the CO₂ numbers into perspective:

Earth's atmosphere: 430 ppm and rising due to fossil fuel burning.
Indoor spaces: <700 ppm is well-ventilated, <1000 ppm is acceptable.
Health effects: >1500 ppm: Causes drowsiness, headaches and reduced cognitive performance.

So for now my solution is simple (but far from ideal): I open a window for five to ten minutes every hour. Yes, even in freezing winter temperatures or during scorching summer heat. It works, but it’s not exactly energy-efficient.