Emission rate of carbon dioxide while sleeping

Abstract

Humans emit carbon dioxide (CO2) as a product of their metabolism. Its concentration in buildings is used as a marker of ventilation rate (VR) and degree of mixing of supply air, and indoor air quality (IAQ). The CO2 emission rate (CER) may be used to estimate the ventilation rate. Many studies have measured CERs from subjects who were awake but little data are available from sleeping subjects and the present publication was intended to reduce this gap in knowledge. Seven females (29 ± 5 years old; BMI: 22.2 ± 0.8 kg/m2) and four males (27 ± 1 years old; BMI: 20.5 ± 1.5 kg/m2) slept for four consecutive nights in a specially constructed capsule at two temperatures (24 and 28°C) and two VRs that maintained CO2 levels at ca. 800 ppm and 1700 ppm simulating sleeping conditions reported in the literature. The order of exposure was balanced, and the first night was for adaptation. Their physiological responses, including heart rate, pNN50, core body temperature, and skin temperature, were measured as well as sleep quality, and subjective responses were collected each evening and morning. Measured steady‐state CO2 concentrations during sleep were used to estimate CERs with a mass‐balance equation. The average CER was 11.0 ± 1.4 L/h per person and was 8% higher for males than for females (P < 0.05). Increasing the temperature or decreasing IAQ by decreasing VR had no effects on measured CERs and caused no observable differences in physiological responses. We also calculated CERs for sleeping subjects using the published data on sleep energy expenditure (SEE) and Respiratory Quotient (RQ), and our measured CERs confirmed both these calculations and the CERs predicted using the equations provided by ASHRAE Standard 62.1, ASHRAE Handbook, and ASTM D6245‐18. The present results provide a valuable and helpful reference for the design and control of bedroom ventilation but require confirmation and extension to other age groups and populations.

Development and application of an indoor carbon dioxide metric

“…There have been a small number of recent studies in which measured CO 2 generation rates from humans have been compared with predictions based on Equation 4. The level of agreement between measurements and predictions is variable, but it should be noted that the predictions are highly dependent on the assumed value of M and that the sample sizes in these studies tend to be small 38,39 . All of the CO 2 generation rates in this paper are based on an air temperature of 296.15 K (23°C).…”

“…The level of agreement between measurements and predictions is variable, but it should be noted that the predictions are highly dependent on the assumed value of M and that the sample sizes in these studies tend to be small. 38,39 All of the CO 2 generation rates in this paper are based on an air temperature of 296.15 K (23°C).…”

Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

“…Humans emit CO 2 mainly through exhalation; dermal emissions could account for only up to 3.5% . The emission rate depends on the metabolic rate, sex, age, and environmental parameters. , Previous studies have reported per-person CO 2 emission rates for adults ranging from 11 L/h during sleeping to ∼80 L/h during physical activities. − Humans can also emit NH 3 through exhalation. − However, dermal emission is the dominating pathway of NH 3 emission, an order of magnitude larger than emission from breath. − NH 3 emission rates range from 0.3 to 12 mg/h per person, depending on the age, clothing coverage, and air temperature. − …”

Prediction of exhaled carbon dioxide concentration using a computer‐simulated person that included alveolar gas exchange

“…Their impact on the CO 2 emission rates has been investigated experimentally in previous studies examining the effects of physical activity, 3–9 age, 8,10 and gender 4,8,9,11 . It has recently been shown that CO 2 emission rates can vary depending on other factors, including air temperature, 10,12–14 the concentration of CO 2 and other pollutants in the inhaled air, 14,15 and psychological effects 16,17 …”

“…1,2 Their impact on the CO 2 emission rates has been investigated experimentally in previous studies examining the effects of physical activity, [3][4][5][6][7][8][9] age, 8,10 and gender. 4,8,9,11 It has recently been shown that CO 2 emission rates can vary depending on other factors, including air temperature, 10,[12][13][14] the concentration of CO 2 and other pollutants in the inhaled air, 14,15 and psychological effects. 16,17 In a previous study, 14 we measured the CO 2 emission rates of six male volunteers who were seated, and therefore, at a low activity level and found that when elevated ambient CO 2 concentration (between 800 and 3000 ppm) was obtained either by restricting ventilation or dosing pure CO 2 from a gas cylinder, the CO 2 emission rate decreased.…”