Gas Sensing Solutions (GSS) found that there are rising levels of carbon dioxide (CO2) in cars, which can vastly increase depending on car capacity.

Feeling drowsy or sleepy whilst driving is a very common occurrence for many. According to a 2005 poll carried out by the American Nation Sleep Foundation, 60% of adult US drivers (around 168 million) admitted to driving whilst feeling drowsy in the past year, with more than one third (around 103 million) admitting to falling asleep behind the wheel.

Levels of CO2 at 1,000 ppm (parts-per-million) and above can cause individuals to become lethargic and drowsy. Carbon dioxide sensor specialists, Gas Sensing Solutions, questioned whether common drowsiness whilst driving could be linked to the build-up of CO2 levels in vehicles.

Scotland-based GSS carried out two different car journey scenarios with a CO2datalogger from its gas sensor range to investigate how the CO2 levels change throughout a car journey. The datalogger used in the experiment measures CO2 concentration, air pressure and temperature, along with relative humidity every few minutes.

“This follows on from our trip to Asia where we used our CO2datalogger to measure CO2 gas levels on planes, trains and taxis. We were surprised that the levels were the worst in taxis - peaking at an astonishing 10,000 ppm on one journey - so we decided to check the levels on our own road trip in the UK,”said Dr. David Moodie, Technical Manager at GSS.

Prior to the car journeys, the CO2 level test was recorded in a stationary car with four passengers with the engine switched off and the windows closed, to avoid flow of fresh air. The CO2 level originally read 100 ppm but soon increased drastically to 4,000 ppm after 15 minutes.

In a moving car with two passengers, the CO2exhaled from their breath increased the overall CO2 concentration to around 1,400 ppm within 45 minutes. After this journey the data logger was left in the vehicle overnight to measure the length of time taken for CO2levels to drop back down (the graph below illustrates this).

CO2 levels recorded with GSS datalogger

Source: GSS

The second car journey consisted of four passengers on a journey from Wales to Scotland. As expected, the CO2 levels increased rapidly with the extra bodies. CO2 levels reached 2,000 ppm in about 20 minutes. This level of CO2 can cause loss of concentration, headaches and sleepiness.

“Our real-world datalogger measurements show how CO2 levels can rapidly build up in an enclosed space with serval occupants,” said Dr. Moodie.

From a 2005 poll by the American Nation Sleep Foundation, out of those who previously admitted to falling asleep at the wheel, 13% they have done so at least once a month. According to data from Australia, England, Finland and other European nations, drowsy driving represents 10-30% of all crashes.