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

Abstract

Background: Associations of higher indoor carbon dioxide (CO2) concentrations with impaired work performance, increased health symptoms, and poorer perceived air quality have been attributed to correlation of indoor CO2 with concentrations of other indoor air pollutants that are also influenced by rates of outdoor-air ventilation.Objectives: We assessed direct effects of increased CO2, within the range of indoor concentrations, on decision making.Methods: Twenty-two participants were exposed to CO2 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, CO2 came from outdoor air and participants’ respiration. Higher concentrations were achieved by injecting ultrapure CO2. 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 CO2 level. Data were analyzed with analysis of variance models.Results: Relative to 600 ppm, at 1,000 ppm CO2, 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 CO2 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.

Sick building syndrome: are we doing enough?

“…Additionally, CO 2 and RH were positively associated with new onset of mucosal, general and school-related symptoms. This was generally supported by Satish et al (2012) who conducted lab-based study using simulated decision-making. The results suggested that CO 2 having a significant detrimental impact at 1000 parts per million (ppm) compared to 600 ppm, despite 1000 ppm being widely considered acceptable.…”

Window and door opening behavior, carbon dioxide concentration, temperature, and energy use during the heating season in classrooms with different ventilation retrofits—ASHRAE RP1624

“…The measured CO 2 concentrations were below the 8-hour maximum permissible occupational exposure level of 5000 ppm (OSHA 2017). Also, there is no conclusive evidence that CO 2 itself among adults should increase the risk of discomfort or health problems or the cognitive performance of simple tasks (Liu et al 2017;Zhang et al 2016Zhang et al , 2017, although demanding cognitive tasks have been shown to be affected (Allen et al 2016;Satish et al 2012). CO 2 at the concentrations measured in the current study should thus not be considered a toxic compound.…”

Limitations and requirements for measuring metabolic rates: a mini review

“…In addition, the higher flow rate reduces the CO 2 concentration within the chamber from~0.5 to~0.1%, which is close to normocapnic levels and poses no risk of the cognitive impairment and behavioral changes reported at higher CO 2 concentrations (albeit in humans-no such work has been done in mice or rats to my knowledge). 20,21 ROOM CALORIMETRY AND CONVECTIVE AIR MOVEMENT With some care, it is possible to utilize knowledge of the kinetics of flow-through respirometry to reverse the distortions caused by chamber time constants. This is particularly relevant to human room calorimetry, where chamber ( = room) volumes of 25 000+ liters are common, together with relatively low flow rates in the 30-80 l/min range.…”