A method for CO2 detection includes obtaining a gas sample; exposing a CO2 sensor to the gas sample, where the sensor includes a reversible and selective pH-sensitive nanocomposite sensor element for CO2 detection, and a hydrophobic surface; compensating for humidity and temperature; coupling at least one light source to receive signals from the CO2 sensor and respond to color changes in the sensor by transducing the color change into a light intensity change; measuring flow; and receiving signals from the at least one light source by at least one photodiode which responds to light intensity changes by transducing the light intensity changes into electronic signals representing varying degrees of light intensity.