I am looking to make a home warning system, since I'm going to be installing a pellet stove inside my new garage. I wish to have my Arduino Uno read data from O2 sensor, located inside the smokestack and if the ppm numbers cross a certain threshold, the Uno would let me know if the burning is incomplete. A complete combustion results in just CO2 and H2O, no O2, right? A steady readout on my computer would also be good. Could anyone give advice on what kind of sensor I should use and how I would connect it to the Uno? Could I use a car lambda sensor somehow? Or would it be more efficient to use a CO2 sensor in this case?