Does this work by shining a beam of IR light through a length of air gap, and measuring the absorption in the wave length band that CO2 absorbs? If so, it must require a flow of air through the air gap. And, if that's the case there would be a minimum volume of air around the sensor that would be needed to refresh the air in the gap so it can follow the fluctuations in CO2 content. Or, am I off on a tangent here?