Gas Sensing Solutions Surprised to Find High Levels of CO2 When Travelling

CO₂ sensor specialists, Gas Sensing Solutions (GSS), took a CO₂ datalogger on a business trip from Scotland to Asia to see how the levels of CO₂ changed on different modes of transport throughout the journey. Surprised by how high levels were on occasions, GSS will be doing further investigations in other locations to see how CO₂ levels vary in the real world.

The datalogger used measures CO₂ concentration, air pressure and temperature along with relative humidity every few minutes. It is a custom solution designed and built by GSS and uses one of its low power, ambient air, CozIR^®-A 5000 sensors. This low power consumption enabled the datalogger to record over a 2-week period without needing a change of battery. The other sensors are an NXP MPL3115A2 pressure sensor and a Sensirion SHT21 temperature and humidity sensor.

The graph shows how the CO₂ level in blue and the air pressure level in green fluctuated throughout the journey. It clearly shows increased levels of CO₂ when there are a number of people in a confined space with limited ventilation to remove CO₂ build up. The World Health Organisation^₁ guideline is that CO₂ levels should be below 1000 ppm, and ASHRAE (the American Society of Heating, Refrigeration and Air Conditioning Engineers) says that CO₂ at high concentrations of 5000 ppm can pose a health risk².

The drop in air pressure on the graph shows the part of the journey that was in a plane. The train journeys show particularly high levels of CO₂, where CO₂ levels built up to over 2000 ppm. Similar results are shown from the meeting room. However, perhaps surprisingly the highest CO₂ peaks were during the taxi journeys with two passengers and a driver. This consistently produced levels in excess of the 5000 ppm health risk indicator mark² - and, at one point of the journey, even peaked at 10,000 ppm. This really shows the high levels of CO₂ that people can be exposed to while driving through a busy city.

"Generally, people are still not aware of the problems of high CO₂ concentrations," said Dr David Moodie, Technical Manager at GSS. "That drowsy sensation you often experience in a stuffy meeting room is caused by elevated levels of CO₂. The higher the level and the longer the exposure, the more apparent the effect is on the body. Travelling can often be tiring, leaving you feeling worn out. This real-world data shows how often you can be exposed to high levels of CO₂ without realising it - even in taxis and trains - and this could be a significant factor in how you feel. So, my advice is to open windows whenever possible to let the CO₂ out. Naturally that does not apply on planes!"

1) https://consult.education.gov.uk/capital/bb101-school-design-iaq-comfort-and-ventilation/supporting_documents/DfE%20Ventilation%20guide%20consultation%20draft%2029%2006%202016.pdf  

2) https://www.ashrae.org/File%20Library/Technical%20Resources/Technical%20FAQs/TC-04.03-FAQ-35.pdf