A CO2 detection chamber includes a gas inlet and a gas outlet. A CO2 sensor is housed in the CO2 detection chamber, where the sensor includes a reversible and selective pH-sensitive nanocomposite sensor element for CO2 detection, and a hydrophobic surface. A flowmeter, a thermistor and a humidity sensor operate to read flow and compensate for humidity conditions. A light source is coupled 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. A photodiode receives signals from the light source and responds to light intensity changes by transducing the light intensity changes into electronic signals representing varying degrees of light intensity. Data representing CO2 measurements is transmitted for display to a mobile device.