Carbon dioxide sensor specialists, Gas Sensing Solutions, wondered if drowsy driving could in part be due to a build-up of CO2 gas, because at levels of 1,000 ppm and above people can become drowsy and lethargic.
The first car journey involved two people travelling to the supermarket. The CO2 from their exhaled breath increased the concentration of CO2 in the car cabin to around 1400 ppm. Surprisingly, it only took about forty-five minutes to reach this level, which shows how quickly CO2 levels can rise. The datalogger was then left in the car overnight with the windows closed. The graph shows just how long it takes for the CO2 to disperse from a closed car, taking until around 9am the next day to drop down to nearer ambient levels of CO2.