The most important thing is that you use an NDIR CO2 sensor. The best are in my opinion from SenseAir (e.g. the S8 that we use in our monitors). Then you can also get them from Sensirion, Winsen or Cubic. I believe for normal operations they perform all quite well.
Important is that you can adjust the automatic baseline calibration duration if you operate the sensor in a closed space that does not regularly get fresh air. Ideally put it into a longer period like 30 or 90 days or switch off and manually calibrate it regularly. I believe not many monitors offer that flexibility out of the box.
If you have some basic electronic skills, you can actually look at our open source build instructions and just build the basic monitor with the CO2 module [1].
Important is that you can adjust the automatic baseline calibration duration if you operate the sensor in a closed space that does not regularly get fresh air. Ideally put it into a longer period like 30 or 90 days or switch off and manually calibrate it regularly. I believe not many monitors offer that flexibility out of the box.
If you have some basic electronic skills, you can actually look at our open source build instructions and just build the basic monitor with the CO2 module [1].
[1] https://www.airgradient.com/documentation/diy-v4/