IAQ | IMPACT ON HEALTH AND PRODUCTIVITY DO INDOOR CO2 LEVELS DIRECTLY AFFECT HEALTH OR WORK PERFORMANCE? How do higher CO2 levels impact health and productivity at work? William Fisk, Pawel Wargocki and Xiaojing Zhang summarise ten studies that explore the effect of poor IAQ T his article summarises the findings of 10 recent studies investigating whether increased carbon dioxide (CO2) concentrations with other factors constant influence perceived air quality, health or work performance. Concentrations of CO2 in occupied buildings exceed outdoor concentrations because CO2 is a product of peoples metabolism. Indoor CO2 concentrations are indicators of the rates of building ventilation with outdoor air per person. A higher indoor CO2 concentration is often considered an indicator of poorer indoor air quality (IAQ), although many factors unrelated to indoor CO2 concentrations influence IAQ. When indoor CO2 concentrations increase and decrease, concentrations of other air pollutants emitted from indoor sources particularly bioeffluents from humans may also increase and decrease. Increased indoor CO2 concentrations have often been associated (correlated) with decreases in perceived air quality, increases in acute health symptoms, and reductions in aspects of human performance.1-3 Research before 2012, although often with conditions atypical of normal buildings, indicated that levels of CO2, with other conditions constant, had no significant impact on people s health or performance unless the CO2 concentrations far exceeded the levels found in buildings.4-10 The occupational limit for CO2 in the US is 5,000 parts per million (ppm) for a 40-hour work week.11 So, the previously documented associations of indoor CO2 concentrations with perceived air quality, health symptoms and performance have been attributed to the other indoor air pollutants with changes in concentrations indicated by the changes in indoor concentrations of CO2. Since 2012, ten studies12-23 have investigated whether increases in moderate CO2 concentrations, with other conditions constant, adversely influence perceptions of IAQ, health or cognitive performance in humans. The study features are described in Table 5 on the IAQ Science website,24 and key findings are illustrated in Figure 1. These studies have been performed with subjects in research facilities, enabling CO2 concentrations to be modified by adding pure CO2 to indoor air while maintaining all, or nearly all, other conditions constant. By providing high ventilation rates, these studies have maintained low concentrations of bioeffluents, and in all studies subjects were unaware of the CO2 concentrations. All studies recruited healthy adults, often college-age adults, as subjects. One study employed pilots16, 21 as 66 September 2019 www.cibsejournal.com CIBSE Sep19 pp66-69 CO2 Research v2.indd 66 23/08/2019 16:50