The ambient CO2 concentration has increased by 40% over the last century, up to 400 ppm, and a rise of up to 670 ppm is expected by 2100 (Jacobson et al., 2019). Indoor CO2 levels are higher than ambient CO2 concentrations because of high occupancy levels and limited ventilation (Bandehali et al., 2021; Jacobson et al., 2019).