Carbon dioxide in passenger cabins: Spatial temporal characteristics and 30-year trends.

Carbon dioxide (CO2 ) is an important environmental parameter in aircraft cabins. To understand the most recent, real-time CO2 concentration levels and their key influencing factors in aircraft cabins, we conducted in-flight measurements of 52 randomly selected commercial flights with different aircraft types and durations from August 2017 to August 2019. The spatial temporal characteristics of CO2 concentrations on board were analyzed and summarized. For the flight time scale, the CO2 concentrations during the boarding phase (1680 ± 558 ppmv) were notably higher than that in other phases, whereas the condition of the cruising phase was the lowest in most flights. The flight average CO2 concentrations of the cruising phase were 1253 ± 164 ppmv, and the corresponding estimated outside airflow rates were 6.2 ± 1.3 L/s/p in the economy class across all flights. Single-aisle and twin-aisle flights did not show noticeable differences for the same phases. Relatively uniform CO2 concentrations were observed at different positions of the same class. By comparing the results of this study with those previously reported, CO2 concentrations showed a slightly decreasing trend over the last 30 years. This suggested a slightly increased ventilation rate and potentially superior air quality on board.