High indoor CO₂ concentrations in an office environment increases the transcutaneous CO₂ level and sleepiness during cognitive work

ABSTRACT

The purpose of this study is to perform a multiparametric analysis on the environmental factors, the physiological stress reactions in the body, the measured alertness, and the subjective symptoms during simulated office work. Volunteer male subjects were monitored during three 4-hr work meetings in an office room, both in a ventilated and a non-ventilated environment. The environmental parameters measured included CO₂, temperature, and relative humidity. The physiological test battery consisted of measuring autonomic nervous system functions, salivary stress hormones, blood's CO₂- content and oxygen saturation, skin temperatures, thermal sensations, vigilance, and sleepiness. The study shows that we can see physiological changes caused by high CO₂ concentration. The findings support the view that low or moderate level increases in concentration of CO₂ in indoor air might cause elevation in the blood's transcutaneously assessed CO₂. The observed findings are higher CO₂ concentrations in tissues, changes in heart rate variation, and an increase of peripheral blood circulation during exposure to elevated CO₂ concentration. The subjective parameters and symptoms support the physiological findings. This study shows that a high concentration of CO₂ in indoor air seem to be one parameter causing physiological effects, which can decrease the facility user's functional ability. The correct amount of ventilation with relation to the number of people using the facility, functional air distribution, and regular breaks can counteract the decrease in functional ability. The findings of the study suggest that merely increasing ventilation is not necessarily a rational solution from a technical-economical viewpoint. Instead or in addition, more comprehensive, anthropocentric planning of space is needed as well as instructions and new kinds of reference values for the design and realization of office environments.

KEYWORDS:

• Autonomic nervous system function
• blood gases
• carbon dioxide
• room ventilation
• skin temperatures

Acknowledgments

The authors would like to thank Timo Murtoniemi, Marko Koivisto, Mikko Kallinen, Heli Sistonen, and Sirpa Hyttinen for their valuable assistance conducting the analyses.

Funding

This research project is sponsored by the University Properties of Finland Ltd. and the RYM Indoor Environment Program with the support of the Finnish Funding Agency for Technology and Innovation (TEKES).