You've definitely done your research on these so most of this is for other readers while I kind of pretend I'm narrating to you. You may be aware, but the earth

You've definitely done your research on these so most of this is for other readers while I kind of pretend I'm narrating to you. You may be aware, but the earth is currently at an average of >400ppm right now, so most hobbyists won't need to measure lower than 400ppm. If you want a "cheaper" sensor that does measure all the way to 0ppm, I could suggest this one [0] for $70 at digikey. Realistically I think any solid-state gas sensor is generally going to require calibration with reference gases --- and that totally sucks. For CO2 there are some affordable options but some other gases I've looked at are pretty unreasonable for hobbyists. I've decided that I'm personally okay with inaccuracy as long as it has good repeatability. Your needs may be different, but for me it's not so much that I need to know the exact number, but rather that I need to be able to chart trends/cycles over weekly/monthly timelines. I also accept that my sensors will drift up/down over long timelines and I try to account for that possibility in any analysis I do. It's less than optimal, but as a hobbyist the sacrifices don't completely kill the endeavor. 0: https://rmtplusstoragesenseair.blob.core.windows.net/docs/publicerat/PSP110.pdf https://rmtplusstoragesenseair.blob.core.windows.net/docs/pu...