Tag: air quality

I ran errands and measured the CO2 concentration everywhere I went

I am starting to take my Adanet CO2 concentration monitor everywhere because I want to see which stores, restaurants, and offices have “fresher” air. The other day on December 20, 2022, I visited a BMO Harris bank branch and a Target store, and I took note of the measurements in three locations within my apartment building.

My goal is to take two readings in each location and photograph the second reading. The photograph provides the proof of the reading in the location I specified as well as a timestamp and GPS that only I can see.

I also took an outdoor reading to establish what the ambient level was that day:
421 parts per million (ppm), which is exactly what the global ambient level is!

Keep in mind that a typical reading in my studio apartment is around 650 ppm.

An outdoor reading of 421 ppm, for reference.

BMO Harris bank branch – 115 S LaSalle St

This is a large bank branch with half a dozen teller stations and a significant business banking area. There were two tellers, a handful of other staff, and myself and another customer – the person density was very low.

Reading: 614 parts per million (ppm)

The CO2 reading was 614 ppm at a BMO Harris bank branch in downtown Chicago.

Target – 1 S State St

A busy department store is where I was most excited to take several readings. I took four readings, all on the second floor.

  1. Men’s clothing department, three minutes after entering the store: 646 ppm
  2. Another area in the men’s clothing department, three minutes later: 785 ppm
  3. A dressing room, six minutes after the previous reading: 913 ppm
  4. Automotive accessories aisle, 15 minutes after: 961 ppm

To give you another reference point, the readings have regularly exceeded 800 ppm – and have exceeded 1,000 ppm if I burn some food – when I’m cooking in my studio apartment. As I write this from there, the reading is 623 ppm.

I was pleased with these numbers at Target; I’m not an expert on assessing air quality but the Centers for Disease Control writes “that indoor CO2 concentrations no greater than 700 parts per million (ppm) above outdoor CO2 concentrations will satisfy a substantial majority (about 80%) of occupants” in office environments – or about 1,121 ppm.

My apartment building

I took three readings in my apartment building:

  1. One of the two bike rooms: 619 ppm
  2. An elevator (I had to visit a lot of floors to wait until I could get a second reading, which also meant the door opened a lot): 788 ppm
  3. Gym (which has two rooms, and I took the reading in the larger room that had fewer people at the time): 596 ppm

Say hello to Adanet, my new CO2 concentration monitor

I acquired a homemade and open source Adanet carbon dioxide (CO2) monitor from a friend in Chicago and tested it on a short trip on the Brown Line ‘L’. The Adanet monitors the concentration of CO2 in the air, in parts per million, which is a proxy for how “fresh” the surrounding air is.

Monitoring CO2 concentration became a more common activity and point of discussion since the COVID-19 pandemic began. A key way to reduce risk of transmission is to have “fresher” air. I’ll establish that “fresher” air is replacing air that has people’s outgoing CO2 with air that has less CO2, namely outdoor air.

(Another reason to monitor CO2? Excessive CO2 can lead to a decline in cognitive ability and sleep quality.)


I conducted an unscientific test of the “freshness” of the air inside a single Brown Line car on my trip between the Western and Belmont stations. I took five readings, which was the most I could take given that the Adanet refreshes every three minutes.

Map showing gray markers indicating where readings were taken. The trip started at the Western Brown Line station and the last reading was taking just before the train pulled into the Belmont station.

The ambient global measurement of CO2 is 421 ppm, measured in May 2022.

On the transit trip, the lowest reading was 475 ppm, which was taken while the device was in my coat pocket before I boarded the train at the outdoor station.

The highest reading was 680 ppm, when the train car had the most people on it during my short trip.


I have been checking the Adanet since getting home two hours ago.

  • I left it in the hallway outside my apartment and a single reading was 556 ppm.
  • Inside my studio readings have been around 650±20 ppm.
  • The highest reading since I got home has been 830 ppm and this is because I partially burned a quesadilla, releasing additional carbon into the air (my standalone air filter also turned on automatically to deal with the reduction in air quality).
  • I opened the balcony door to let fresh air in and 15 minutes later the reading dropped to between 671 and 692 ppm (the more readings the better).