| I've seen references to this sensor before and find it a bit concerning that there's no information about how to properly use the CO2 sensor. This sensor uses a SenseAir S8, which like most CO2 sensors, has an automatic baseline calibration algorithm enabled [0], which expects to see pure, undiluted fresh air at least once every 8 days. The only way to disable it is explicitly, through the MODBUS interface [1]. Leaving it enabled makes perfect sense in a business or businesslike environment because these environments will be completely unoccupied overnight and have air conditioning, which usually does a daily fresh-air purge, ensuring that the sensor will have regular exposure to fresh air. However in a residential environment, the auto baseline calibration often doesn't make sense, especially in winter. When the windows are closed and/or people or pets are around, it's very rare for the sensor to see uncontaminated fresh air, so it will see say 500ppm of CO2 and assume it's fresh air when it really isn't. I have measured this and it's a real problem. In a residential environment, unless you're sure you have good, frequent exposure to pure fresh air, you're better off doing a fixed calibration once a year or so. AirGradient also seems to be a hardware-only design. The ESPHome project [2] has great software support for a variety of sensors (including the SenseAir S8, so it should be compatible with the AirGradient hardware) as well as a very well-documented hardware project [3]. After trying my own Arduino-based software and then ESP-IDF, I find esphome much more pleasant to work with. [0]: https://rmtplusstoragesenseair.blob.core.windows.net/docs/pu... [1]: https://rmtplusstoragesenseair.blob.core.windows.net/docs/De... [2]: https://esphome.io/ [3]: https://github.com/nkitanov/iaq_board |