TA-23-C039 – Evaluation of Suitability of CO2 Measuring Devices in Practice with a Focus on Measuring Accuracy

Compact CO₂ monitoring devices are increasingly being used to evaluate indoor air quality and the effectiveness of air change in indoor spaces, particularly with respect to manual window ventilation. In the past two years, CO₂-levels in indoor air have also been used as a proxy for assessing the risk of airborne transmission of SARS-CoV-2. Now, due to energy-saving regulations in Europe following an energy shortage, CO₂ is also being used to monitor minimal hygienic air change rates in densely occupied rooms. Compared to earlier research, CO₂ sensor technology has improved significantly over the last decade. However, the accuracy and reliability of current commercially available CO₂ measuring devices remain a concern. To address this issue, a lab measurement project was conducted to test the performance of 13 device types in terms of CO₂, temperature and humidity deviation, measured at various operating points. The results showed that 11 of the 13 CO₂ device types examined met the requirements of a measurement deviation of no more than 10% CO₂ for all operating points tested. Conversely, some test devices showed deviations of over 100%. Furthermore, differences were found when testing with dry or humidified challenge gas. As previously reported in the literature, both temperature and humidity can affect CO₂ readings, with a range of ± 20 ppmv up to ± 120 ppmv. In conclusion, before purchasing a CO₂ measuring device, it is recommended to consult independent test reports and request independent lab reports.