Accuracy verification of low-cost CO2 concentration measuring devices for general use as a countermeasure against COVID-19

Within the context of the COVID-19 pandemic, CO2 sensors that measure ventilation conditions and thereby reduce the risk of airborne infection, are gaining increasing attention. We investigated and verified the accuracy of 12 relatively low-cost sensor models that retail for less than $45 and are advertised as infection control measures on a major e-commerce site. Our results indicate that 25% of the tested sensors can be used to identify trends in CO2 concentration, if correctly calibrated. However, 67% of sensors did not respond to the presence of CO2, which suggests that a type of pseudo-technique is used to display the CO2 concentration. We recommend that these sensors are not suitable for infection prevention purposes. We also found that all 67% of the sensors that did not respond to CO2 responded strongly to alcohol. Owing to the widespread use of alcohol in preventing the spread of infectious diseases, sensors that react to alcohol can display inaccurate values, resulting in inappropriate ventilation behavior. Therefore, we strongly recommended that these sensors not be used. Based on our results, we offer practical recommendations to the average consumer, who does not have special measuring equipment, on how to identify inaccurate CO2 sensors.