In the 1970s, Bosch created the first automotive oxygen sensor that when incorporated into closed loop emission control systems helped to dramatically reduce vehicle emissions. Now Bosch has created a new carbon dioxide sensor for use in climate control systems inside the car. By measuring the CO2 inside the vehicle when the air conditioning is running, the system automatically switches to recirculation mode whenever possible. Only when the CO2 level exceeds a threshold is fresh outside air added. By optimizing the use of recirculation mode, the system minimizes the load on the air conditioning compressor and improves fuel efficiency. The carbon dioxide sensor used infrared-based spectroscopy to measure CO2 levels in the air.