%0 Journal Article
%K Indoor environmental quality (IEQ)
%K Ventilation
%K Carbon dioxide
%K Decision Making
%K Cognition
%K Human performance
%A Usha Satish
%A Mark J Mendell
%A Krishnamurthy Shekhar
%A Toshifumi Hotchi
%A Douglas P Sullivan
%A Siegfried Streufert
%A William J Fisk
%B Environmental Health Perspectives
%D 2012
%N 12
%P 1671-1677
%R 10.1289/ehp.1104789
%T Is CO<sub>2</sub> an Indoor Pollutant? Direct Effects of Low-to-Moderate CO<sub>2</sub> Concentrations on Human Decision-Making Performance
%V 120
%2 LBNL-6196E
%8 12/2012
%! Environ Health Perspect.
%X <h2>BACKGROUND:</h2><p>Associations of higher indoor carbon dioxide (CO<sub>2</sub>) concentrations with impaired work performance, increased health symptoms, and poorer perceived air quality have been attributed to correlation of indoor CO<sub>2</sub> with concentrations of other indoor air pollutants that are also influenced by rates of outdoor-air ventilation.</p><h2>OBJECTIVES:</h2><p>We assessed direct effects of increased CO<sub>2</sub>, within the range of indoor concentrations, on decision making.</p><h2>METHODS:</h2><p>Twenty-two participants were exposed to CO<sub>2</sub> at 600, 1,000, and 2,500 ppm in an office-like chamber, in six groups. Each group was exposed to these conditions in three 2.5-hr sessions, all on 1 day, with exposure order balanced across groups. At 600 ppm, CO<sub>2</sub> came from outdoor air and participants' respiration. Higher concentrations were achieved by injecting ultrapure CO<sub>2</sub>. Ventilation rate and temperature were constant. Under each condition, participants completed a computer-based test of decision-making performance as well as questionnaires on health symptoms and perceived air quality. Participants and the person administering the decision-making test were blinded to CO<sub>2</sub> level. Data were analyzed with analysis of variance models.</p><h2>RESULTS:</h2><p>Relative to 600 ppm, at 1,000 ppm CO<sub>2</sub>, moderate and statistically significant decrements occurred in six of nine scales of decision-making performance. At 2,500 ppm, large and statistically significant reductions occurred in seven scales of decision-making performance (raw score ratios, 0.06-0.56), but performance on the focused activity scale increased.</p><h2>CONCLUSIONS:</h2><p>Direct adverse effects of CO<sub>2</sub> on human performance may be economically important and may limit energy-saving reductions in outdoor air ventilation per person in buildings. Confirmation of these findings is needed.</p>