Measuring Complex for Carbon-Dioxide Monitoring in Air

We describe the advantages and disadvantages of infrared and electrochemical gas analyzers of carbon dioxide (CO₂). We study the possibility of application of conductometric sensors with distilled water for the purposes of monitoring of the CO₂ content in air. We manufactured two identical measuring systems each of which contains two open-type conductometric cells, a matching device, and a personal computer. With the help of these complexes, we performed the experiments aimed at simultaneous measurements of the CO₂ content in air at two sites (in a laboratory room and in a building located in the forest at a distance of 15 km from the first site) with knowingly different daily dynamics of variations of the CO₂ level. We carried out special experiments aimed at the determination of the time lag of conductometric cells and evaluation of the conversion factor of the obtained levels of CO₂ content into the standard measurement units. It is shown that the daily dynamics of variations of the electric conductivity of distilled water in the open cells agrees with the expected dynamics of changes in the CO₂ content in the rooms used for measurements. The serviceability of the analyzed measuring complex is confirmed and the possibility of creation of a device based on this complex and intended for the long-term monitoring of the CO₂ content in the air mixture of gases is demonstrated. The high selectivity of the proposed measuring complex to the presence of CO₂ (as compared with the other atmospheric gases) is established.