Carbon dioxide generation rates for building occupants

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Abstract

Indoor carbon dioxide (CO 2) concentrations have been used for decades to characterize building ventilation and indoor air quality. Many of these applications require rates of CO 2 generation from the building occupants, which are currently based on approaches and data that are several decades old. However, CO 2 generation rates can be derived from well-established concepts within the fields of human metabolism and exercise physiology, which relate these rates to body size and composition, diet, and level of physical activity. This paper reviews how CO 2 generation rates have been estimated in the past and discusses how they can be characterized more accurately. Based on this information, a new approach to estimating CO 2 generation rates is presented, which is based on the described concepts from the fields of human metabolism and exercise physiology. Using this approach and more recent data on body mass and physical activity, values of CO 2 generation rates from building occupants are presented along with the variability that may occur based on body mass and activity data.

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Most cited references 13

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Associations between classroom CO2 concentrations and student attendance in Washington and Idaho.

D. G. Shendell, R Prill, W J Fisk … (2004)

Student attendance in American public schools is a critical factor in securing limited operational funding. Student and teacher attendance influence academic performance. Limited data exist on indoor air and environmental quality (IEQ) in schools, and how IEQ affects attendance, health, or performance. This study explored the association of student absence with measures of indoor minus outdoor carbon dioxide concentration (dCO(2)). Absence and dCO(2) data were collected from 409 traditional and 25 portable classrooms from 22 schools located in six school districts in the states of Washington and Idaho. Study classrooms had individual heating, ventilation, and air conditioning (HVAC) systems, except two classrooms without mechanical ventilation. Classroom attributes, student attendance and school-level ethnicity, gender, and socioeconomic status (SES) were included in multivariate modeling. Forty-five percent of classrooms studied had short-term indoor CO(2) concentrations above 1000 p.p.m. A 1000 p.p.m. increase in dCO(2) was associated (P < 0.05) with a 0.5-0.9% decrease in annual average daily attendance (ADA), corresponding to a relative 10-20% increase in student absence. Annual ADA was 2% higher (P < 0.0001) in traditional than in portable classrooms. This study provides motivation for larger school studies to investigate associations of student attendance, and occupant health and student performance, with longer term indoor minus outdoor CO(2) concentrations and more accurately measured ventilation rates. If our findings are confirmed, improving classroom ventilation should be considered a practical means of reducing student absence. Adequate or enhanced ventilation may be achieved, for example, with educational training programs for teachers and facilities staff on ventilation system operation and maintenance. Also, technological interventions such as improved automated control systems could provide continuous ventilation during occupied times, regardless of occupant thermal comfort demands.

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Effects of exposure to carbon dioxide and bioeffluents on perceived air quality, self-assessed acute health symptoms, and cognitive performance.

X. Zhang, P Wargocki, Z Lian … (2017)

The purpose of this study was to examine the effects on humans of exposure to carbon dioxide (CO2 ) and bioeffluents. In three of the five exposures, the outdoor air supply rate was high enough to remove bioeffluents, resulting in a CO2 level of 500 ppm. Chemically pure CO2 was added to this reference condition to create exposure conditions with CO2 at 1000 or 3000 ppm. In two further conditions, the outdoor air supply rate was restricted so that the bioeffluent CO2 reached 1000 or 3000 ppm. The same 25 subjects were exposed for 255 min to each condition. Subjective ratings, physiological responses, and cognitive performance were measured. No statistically significant effects on perceived air quality, acute health symptoms, or cognitive performance were seen during exposures when CO2 was added. Exposures to bioeffluents with CO2 at 3000 ppm reduced perceived air quality; increased the intensity of reported headache, fatigue, sleepiness, and difficulty in thinking clearly; and reduced speed of addition, the response time in a redirection task, and the number of correct links made in the cue-utilization test. This suggests that moderate concentrations of bioeffluents, but not pure CO2 , will result in deleterious effects on occupants during typical indoor exposures.