As with many others I have started spending most of my time in my apartment recently. I became interested in what this immobility might be doing to the composition of the air I breathe.

There is a page on the United States CDC site documenting “Immediately Dangerous to Life or Health Concentration” (IDLH) levels. The page indicates 50,000 ppm produces extremely dangerous results, while the OSHA “Permissible Exposure Limit” (long term exposure) is much lower at 5,000 ppm.

I purchased a CO2 meter off of amazon for a little over $100, with the capability to log over USB.

CO2 Meter

Upon booting the device it immediately started emitting a loud alarm, which by default went off over 2,000 ppm. By standard guidelines this is not overtly dangerous, though it might not be ideal either. In the open air the level is around 400 ppm, my apartment was many times above that.

I am a minimalist and own very few possessions, not needing much space I rent a studio under 200 square feet. During the recent California fires the external air was full of the after effects making the bay area temporarily one of the most polluted (air anyways) places on earth. I got in the habit of keeping my windows sealed, and an air filter running. However now that the air is substantially cleaner this might not be an ideal trade off. In the confined space the CO2 level can increase a couple hundred ppm an hour.

A few studies have been done to determine what cognitive effects might exist inside the safe range of CO2 found indoors. This 2012 Berkeley study, found extreme effects across a variety of tests (p < 0.001), although N = 22. Another 2016 study had strong effects (p < 0.0001, N=24). A 2018 study on submariners finds no effect (N = 9) even at much higher levels.

Large effect sizes can alleviate needing a large number participants (for example 100% of people taking X drug dying within an hour), but it would be nice if there was more clarity. I don’t see data to indicate high CO2 concentration to be beneficial to health and cognition, so assuming that it is harmful seems the safer play.

I bought a window fan to increase air circulation. This seems to do better than just keeping the Window open, and now my apartment stays 400-600 ppm. I don’t plan to attempt any quantified self style studies at the moment, but I might start persistent a log for the fun of it. I can subjectively say keeping the window open feels better but I can’t say it has anything to do with CO2, and I can’t easily blind myself to what state the apartment is in.