I've had success with the Cozair sensors from Gas Sensing Solutions. At the time I started looking at CO2 sensors a couple of years ago they were pretty much one of the few and the lowest cost sensor. Now there are others available using the same technologies. The sensor I have is now connected to a Lopy and Expansion board to provide regular readings via LoRa. Andrew

I asked them back in October. They asked 99USD/piece for 100pcs order quantity. Unless it goes to half that price I believe it is not suitable for mass market IoT products. Maybe if you would approach SenseAir directly the price would be better. Anyway if you are going to test it I would be very interested in the results. We are currently using Sensirion SCD30 which has high power consumption (basically you have to perform more than 10 consequent measurements) but the results are pretty good and so is the price.