All CO2 concentrations and RMSE metrics are measured in ppm and not ppb as stated in the published version (Table 2, 3, 4, 5, 6 and Figure 5.c, 5.d).
The errors have no effect on the results and conclusion of the paper and have been fixed in the pdf-version available here.
In Section 3 we list different VOC emssision sources that cause human interference on the two MOX sensors used in the measurement study.
There are potentially more factors causing notable interference on the sensors.
Namely, 1) humidity and temperature changes due to the closeness to the body and 2) hydrogen (H2), which is a component of human breath and a cross-sensitivity of the sensors.