Came here to say something similar. I expected an actual circuit build (of which there are many), but this is just plugging in a USB data logging CO2 monitor (which is $116 on Amazon right now, but apparently the normal price is ~$70 USD) and using it with Prometheus. I've done something similar wrapping https://github.com/merbanan/rtl_433 to pick up temp / humidity monitoring data from sensors around my home, then stuffing the results into InfluxDB and using Kapacitor for alerting (sends me an email when my freezer gets too hot) + Chronograf for graphing. It took an evening of reading docs and messing around to get it all working, and I'd recommend Ding I Y if it sounds cool -- you'll very likely learn something. Note that you could do the same with an ELK stack or Sensu or Nagios or whatever you want to play with.
They’re all Acurite sensors with lithium batteries (Energizer ultimate lithium, available at Target on sale sometimes and other places). The one in the freezer is a “00592TXR” and lasts ~9 months in there IIRC (lithium cells do much better with cold temps than alkaline). I also have a few model 06044 which are small temp + humidity sensors with a display. These also have good battery life. Lastly, Acurite makes a smart hub to log to their cloud, model 09150M. I haven’t set it up yet, but it basically does the same stuff: https://www.myacurite.com/#/login
I’ve also had an Acurite display with some segments of digits that looked funky depnending on viewing angle. It was usable but kind of bugged me. I contacted them and they RMAd it quickly and easily for me (they just sent a new unit). For this reason, their easy availability on Amazon, the reliability and battery life I’ve had with half a dozen of their sensors deployed in and outdoors, I’ll keep buying them when I need this type of thing in the future. They don’t ever lock up or need fiddling with, so they’re kind of boring in that they just keep working until the batteries go flat. The widespread open source support is also certainly nice :)
AcuRite Access looked very interesting, until I found that it needs a phyical cable to the router. I am trying to move away from cables, as does most of the world. A bit disappointing for a 'New !' product.
Which does not monitor CO₂ content. VOC mostly is an issue with new furniture and can lead to Sick Building Syndrom. CO₂ is an independent issue you will always have with people in the room that breath.