carbon dioxide sensor gas sensors hazardous gas detection CARBON DIOXIDE SENSOR To maintain a healthy environment in an enclosed vehicular facility, install the carbon dioxide sensor to start the exhaust fans and open fresh air dampers when the CO concentration rises to prescribed levels, normally 25 or 35 PPM based on local building codes. By using demand-based ventilation control you can save up to 70% of the energy costs when compared to running the fans full time, especially in hot or cold climates where heating or cooling is an added expense.