Literature Survey on the Effects of Pure Carbon Dioxide on Health, Comfort and Performance

Carbon dioxide (CO₂) is one of the components of the earth atmosphere. It is also a significant human metabolite. It is colourless and odourless gas. The background levels of CO₂ in ambient air are about 350-400 ppm. Its concentration in buildings can be an order of magnitude higher reaching even 4,000-4,500 ppm (Menå and Larsen, 2010). The indoor levels of CO₂ depend mainly on human occupancy (CO₂ producing processes) and the frequency of air renewal (outdoor air exchange rate). Since studies of Pettenkofer in the 19th century, the levels of indoor CO₂ have been used as an indicator of air quality in buildings (Pettenkofer, 1858), as well as quantity and effectiveness of ventilation in the presence of people; the levels above 1,000 ppm have been generally considered to cause unacceptable air quality; the levels above 2,000 ppm are considered as the levels requiring actionable decisions. The 8-hour permissible occupational exposure level to CO₂ is set at 5,000 ppm (ACGIH, 2011). Although in many studies CO₂ has been related with health symptoms, comfort and performance of office work and schoolwork, it in itself has traditionally been assumed innocuous at the typical levels indoors; in these studies, CO₂ was merely a proxy for elevated exposure levels to air pollutants, and an indicator of inadequate outdoor air ventilation and poor indoor air quality. Two recent experiments suggest however that the exposure to pure CO₂ at the levels typically occurring indoors and lower than the levels prescribed as permissible by the occupational standards can have negative effects on some aspects of human performance, in particular on tasks requiring concentration (Kajtar et al., 2006) and on tasks, in which decision should be taken (Satish et al., 2012). The present paper reports the results of the literature survey aimed to summarize the published evidence on the effects of pure CO₂ on humans and, if possible, to suggest the underlying mechanisms.