I highly recommend Dual-NDIR sensors that bring their own volume of calibration gas. Auto calibration is not practical in any serious indoor monitoring use case.
How would that work? Having one sensor sealed with reference gas does nothing to help the second sensor. Is there actually a dual sensor which shuttles the gas between them? Seems complicated.
it's a 2nd sealed chamber and shares some sensor parts. Some parts are different, so it's not perfect of course, but much better as the requirement of regular manual calibration. Sensirion SCD30 for example, where you can even see the Y shape of the gas chambers.
