Gas Sensing Solutions investigates levels of CO2 on car journeys

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

Before the datalogger took to the road, it was first used to test CO₂ levels in a stationary car. This would show the impact on CO₂ levels with a group of four people in a confined space. The engine was switched off and the windows kept closed to avoid any flow of fresh air inside the vehicle.

The datalogger showed that when the passengers got inside the car, the CO₂ level was 1,000ppm. It then rocketed to almost 4,000ppm in just 15 minutes. At that stage, the atmosphere inside the cabin had become extremely stuffy and unpleasant.

Next came the road trip. 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 1,400ppm.

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.

The second car journey recorded four people travelling non-stop from Wales to Scotland. With four people, the level of CO₂ shot up even faster, reaching 2,000ppm in about twenty minutes. This is the level where CO₂ symptoms can start to cause loss of concentration, headaches and sleepiness for example. Fortunately, they opened the windows to bring in fresh air from outside, which reduced the CO₂ to more acceptable, ambient levels within an hour.

Dr David Moodie, added: "Our real world datalogger measurements show how CO₂ levels can rapidly build up in an enclosed space with several occupants - and in a relatively short space of time too. The results on both journeys exceeded The World Health Organisation guideline that CO₂ levels should be below 1,000ppm."

The datalogger used in the experiment measures CO₂ concentration, air pressure and temperature, along with relative humidity every few minutes. This unit was designed and built by GSS and it uses one of its low power, ambient air, CozIR-A sensors. GSS's unique LED technology at the heart of its sensors means that it has a very low power consumption, unlike many other CO₂ sensors that need mains power.

This enables battery-powered CO₂ monitoring products to be created, such as this datalogger, that is able to record over a two week period without needing a change of battery.

Dr David Moodie, concluded: "This ability to be battery powered for long periods has opened up a whole new range of design possibilities for CO₂ monitors. Now it's possible to have handheld breath monitors with high speed sensing for people with respiratory conditions, portable leak detection instruments, handheld MAP analysers, and wireless air quality monitors for IoT applications. These are just a few examples of what is achievable, the possibilities really are endless."

Drowsy driving facts and stats
According to a 2005 poll by the American National Sleep Foundation, 60% of adult US drivers - about 168 million people - said that they have driven a vehicle while feeling drowsy in the past year.

More than one-third, (37% or 103 million people), have actually fallen asleep at the wheel. Of those who have nodded off, 13% say 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.