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I am working with an Arduino Nicla Sense ME to measure indoor air quality. Unfortunately the resulting values are far off realistic CO2 PPM values. When starting the controller the co2_eq values stay at 500 for about 5 minutes. After that they jump to 400 and increasing. That seems to be standard procedure. In a room with around 700 PPM CO2 (external CO2 monitor) the Nicla's co2_eq values are around 1000-2000. It drops to around 500 when opening the windows. But it also increased to over 1000 immediately after closing. I also started to train the sensor with extreme values for 30 Minutes. I put it in a box with fresh air and put it outside. And i put it in a box with the smoke of a matchstick. After that the values are over 3000 and stay there for hours. The documentation writes: The IAQ scale ranges from 0 (clean air) to 500 (heavily polluted air). During operation, the algorithms automatically calibrate and adapt themselves to the typical environments where the sensor is operated (e.g., home, workplace, inside a car, etc.). This automatic background calibration ensures that users experience consistent IQ performance. The calibration process considers the recent measurement history (typ. up to four days, configurable) to ensure that IAQ ~ 50 corresponds to "typical good" air and IAQ ~ 200 indicates "typical polluted" air. Is the "recent measurement history" saved or does it start with a reboot / flash from zero? How many hours and which conditions are needed to get realistic values? ... View more