Using EEG to characterise drowsiness during short duration exposure to elevated indoor carbon dioxide concentrations

Drowsiness which can affect work performance, is often elicited through self- reporting. This paper demonstrates the potential to use EEG to objectively quantify changes to drowsiness due to poor indoor air quality. Continuous EEG data was recorded from 23 treatment group participants subject to artificially raised indoor CO2 concentrations (average 2,700 textpm 300 ppm) for approximately 10 minutes and 13 control group participants subject to the same protocol without additional CO2 (average 830 textpm 70 ppm). EEG data were analysed for markers of drowsiness according neurophysiological methods at three stages of the experiment, Baseline, High CO2 and Post-Ventilation. Treatment group participants' EEG data yielded a closer approximation to drowsiness than that of control group participants during the High CO2 condition, despite no significant group differences in self-reported sleepiness. Future work is required to determine the persistence of these changes to EEG over longer exposures and to better isolate the specific effect of CO2 on drowsiness compared to other environmental or physiological factors.Practical implicationsThis study introduces EEG as a potential objective indicator of the effect of indoor environmental conditions upon drowsinessParticipants exposed to 2,700 ppm for 10 minutes showed greater evidence of a progression towards drowsiness (as measured by EEG) than that of participants who received the same protocol without additional CO2 (mean 830 textpm 70 ppm), despite similar ratings of subjective sleepiness.Subjective and objectively measured indications of drowsiness were reduced following ventilation of the room. Future work could explore the potential of regular ventilation episodes in knowledge work spaces to retain alertness