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      Is CO 2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO 2 Concentrations on Human Decision-Making Performance

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          Abstract

          Background: Associations of higher indoor carbon dioxide (CO 2) concentrations with impaired work performance, increased health symptoms, and poorer perceived air quality have been attributed to correlation of indoor CO 2 with concentrations of other indoor air pollutants that are also influenced by rates of outdoor-air ventilation.

          Objectives: We assessed direct effects of increased CO 2, within the range of indoor concentrations, on decision making.

          Methods: Twenty-two participants were exposed to CO 2 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 2 came from outdoor air and participants’ respiration. Higher concentrations were achieved by injecting ultrapure CO 2. 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 2 level. Data were analyzed with analysis of variance models.

          Results: Relative to 600 ppm, at 1,000 ppm CO 2, 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.

          Conclusions: Direct adverse effects of CO 2 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.

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          Association of ventilation rates and CO2 concentrations with health and other responses in commercial and institutional buildings.

          O. A. Seppanen, W J Fisk, M J Mendell (1999)
          This paper reviews current literature on the associations of ventilation rates and carbon dioxide concentrations in non-residential and non-industrial buildings (primarily offices) with health and other human outcomes. Twenty studies, with close to 30,000 subjects, investigated the association of ventilation rates with human responses, and 21 studies, with over 30,000 subjects, investigated the association of carbon dioxide concentration with these responses. Almost all studies found that ventilation rates below 10 Ls-1 per person in all building types were associated with statistically significant worsening in one or more health or perceived air quality outcomes. Some studies determined that increases in ventilation rates above 10 Ls-1 per person, up to approximately 20 Ls-1 per person, were associated with further significant decreases in the prevalence of sick building syndrome (SBS) symptoms or with further significant improvements in perceived air quality. The carbon dioxide studies support these findings. About half of the carbon dioxide studies suggest that the risk of sick building syndrome symptoms continued to decrease significantly with decreasing carbon dioxide concentrations below 800 ppm. The ventilation studies reported relative risks of 1.5-2 for respiratory illnesses and 1.1-6 for sick building syndrome symptoms for low compared to high low ventilation rates.
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            Physiological impact of the N95 filtering facepiece respirator on healthcare workers.

            Raymond Roberge, Aitor Coca, W Jon Williams … (2010)
            To assess the physiological impact of the N95 filtering facepiece respirator (FFR) on healthcare workers. Ten healthcare workers each conducted multiple 1-hour treadmill walking sessions, at 1.7 miles/h, and at 2.5 miles/h, while wearing FFR with exhalation valve, FFR without exhalation valve, and without FFR (control session). We monitored heart rate, respiratory rate, tidal volume, minute volume, blood oxygen saturation, and transcutaneously measured P(CO2). We also measured user comfort and exertion, FFR moisture retention, and the carbon dioxide and oxygen concentrations in the FFR's dead space. There were no significant differences between FFR and control in the physiological variables, exertion scores, or comfort scores. There was no significant difference in moisture retention between FFR with and without exhalation valve. Two subjects had peak P(CO2) > or = 50 mm Hg. The FFR with exhalation valve offered no benefit in physiological burden over the FFR without valve. The FFR dead-space oxygen and carbon dioxide levels did not meet the Occupational Safety and Health Administration's ambient workplace standards. In healthy healthcare workers, FFR did not impose any important physiological burden during 1 hour of use, at realistic clinical work rates, but the FFR dead-space carbon dioxide and oxygen levels were significantly above and below, respectively, the ambient workplace standards, and elevated P(CO2) is a possibility. Exhalation valve did not significantly ameliorate the FFR's P(CO2) impact.
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              The effects of outdoor air supply rate in an office on perceived air quality, sick building syndrome (SBS) symptoms and productivity.

              I G Clausen, J Sundell, B Fanger … (2000)
              Perceived air quality, Sick Building Syndrome (SBS) symptoms and productivity were studied in a normally furnished office space (108 m3) ventilated with an outdoor airflow of 3, 10 or 30 L/s per person, corresponding to an air change rate of 0.6, 2 or 6 h-1. The temperature of 22 degrees C, the relative humidity of 40% and all other environmental parameters remained unchanged. Five groups of six female subjects were each exposed to the three ventilation rates, one group and one ventilation rate at a time. Each exposure lasted 4.6 h and took place in the afternoon. Subjects were unaware of the intervention and remained thermally neutral by adjusting their clothing. They assessed perceived air quality and SBS symptoms at intervals, and performed simulated normal office work. Increasing ventilation decreased the percentage of subjects dissatisfied with the air quality (P < 0.002) and the intensity of odour (P < 0.02), and increased the perceived freshness of air (P < 0.05). It also decreased the sensation of dryness of mouth and throat (P < 0.0006), eased difficulty in thinking clearly (P < 0.001) and made subjects feel generally better (P < 0.0001). The performance of four simulated office tasks improved monotonically with increasing ventilation rates, and the effect reached formal significance in the case of text-typing (P < 0.03). For each two-fold increase in ventilation rate, performance improved on average by 1.7%. This study shows the benefits for health, comfort and productivity of ventilation at rates well above the minimum levels prescribed in existing standards and guidelines. It confirms the results of a previous study in the same office when the indoor air quality was improved by decreasing the pollution load while the ventilation remained unchanged.
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                Author and article information

                Journal
                Journal ID (nlm-ta): Environ Health Perspect
                Journal ID (publisher-id): EHP
                Title: Environmental Health Perspectives
                Publisher: National Institute of Environmental Health Sciences
                ISSN (Print): 0091-6765
                ISSN (Electronic): 1552-9924
                Publication date (Electronic): 20 September 2012
                Publication date (Print): December 2012
                Volume: 120
                Issue: 12
                Pages: 1671-1677
                Affiliations
                [1 ]Department of Psychiatry and Behavioral Science, Upstate Medical University, State University of New York, Syracuse, New York, USA
                [2 ]Indoor Environment Department, Lawrence Berkeley National Laboratory, Berkeley, California, USA
                Author notes
                Address correspondence to M.J. Mendell, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., 90R3058, Berkeley, CA 94720 USA. Telephone: (510) 486-5762. Fax: (510) 486-6658. E-mail: mjmendell@ 123456lbl.gov
                Article
                Publisher ID: ehp.1104789
                DOI: 10.1289/ehp.1104789
                PMC ID: 3548274
                PubMed ID: 23008272
                SO-VID: bb48950c-9a5e-4d01-a20d-75fc2152b46c
                Copyright statement: Copyright @ 2012
                License:

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, properly cited.

                History
                Date received : 28 November 2011
                Date accepted : 20 September 2012
                Categories
                Subject: Research

                ScienceOpen disciplines: Public health
                Keywords: carbon dioxide,cognition,decision making,human performance,indoor environmental quality,ventilation
                Data availability:
                ScienceOpen disciplines: Public health
                Keywords: carbon dioxide, cognition, decision making, human performance, indoor environmental quality, ventilation

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