Gas Sensing Solutions (GSS), a specialist in making CO2 sensors, carried a CO2 datalogger from Scotland to Asia on a business trip to observe the change in the CO2 levels on different modes of transport through the entire trip. Intrigued by the astonishingly high levels at times, GSS is planning to carry out further analysis in other locations to observe the real-world change in the CO2 levels.
Customized CO2 Datalogger from GSS
The datalogger used has the ability to measure CO2 concentration, temperature, and air pressure together with relative humidity every few minutes. It is a tailored solution designed and developed by GSS and employs one of its low-power, ambient air CozIR®-A sensors. Such a low power consumption allowed the datalogger to record over a two-week period without needing to change the battery. The other sensors used are a Sensirion SHT21 temperature and humidity sensor and an NXP MPL3115A2 pressure sensor.
Datalogger uses a CozIR-A CO2 sensor
The graph in the figure below indicates the fluctuation of the air pressure level in green and the CO2 level in blue through the entire journey. It is evident from the graph that the CO2 levels are elevated when there are more people in a confined space with limited ventilation to eliminate CO2 build-up.
Graph showing CO2 and pressure levels on the trip
The World Health Organization guideline1 states that CO2 levels should be lower than 1000 ppm, and the American Society of Heating, Refrigeration and Air Conditioning Engineers, or ASHRAE, has reported that higher concentrations of CO2 of about 5000 ppm can pose a health risk.2 The decrease in air pressure on the graph indicates the part of the journey made in a plane. Specifically higher levels of CO2 were observed during the train journeys, where the levels increased to more than 2000 ppm. Analogous outcomes are evident from the meeting room. Yet, more astonishingly, the highest CO2 levels were observed as part of the taxi journeys with a driver and two passengers. This invariably generated levels of over 5000 ppm health-risk indicator mark2; at one point of the journey, the levels even reached 10,000 ppm. This actually indicates the elevated levels of CO2 people can be exposed to during a drive through a busy city.
How CO2 levels impact on the human body
Generally, people are still not aware of the problems of high CO2 concentrations. 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!
Dr David Moodie, Technical Manager at GSS
Technology used to make measurements
A majority of the CO2 sensors function by measuring the amount of light absorbed by CO2 molecules in the 4.2–4.4 μm when it passes through the sample gas, which is called non-dispersive infrared (NDIR) absorption. The amount of CO2 that is present is indicated by the extent of absorption. The proprietary LEDs developed by GSS are particularly adjusted to emit at these wavelengths. They use a lesser amount of power and turn on right away, thereby facilitating the sensor readings to be taken within a few seconds. Consequently, GSS has innovated the development of CO2 sensors with the ability to be powered by batteries for a long time of up to 10 years. The sensors developed by competitors are equipped with IR sources that need considerably more power per measurement and also require a longer time period to attain a stable condition for a measurement, leading to the need for mains power.
This information has been sourced, reviewed and adapted from materials provided by Gas Sensing Solutions.
For more information on this source, please visit Gas Sensing Solutions.