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Du B, Reda I, Licina D, Kapsis C, Qi D, Candanedo JA, Li T. Estimating Air Change Rate in Mechanically Ventilated Classrooms Using a Single CO 2 Sensor and Automated Data Segmentation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024. [PMID: 39374375 DOI: 10.1021/acs.est.4c02797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/09/2024]
Abstract
With a growing emphasis on indoor air quality (IAQ) in educational environments, CO2 monitoring in classrooms has become commonplace. CO2 data can be used to estimate outdoor air change rate (ACH) based on the mass balance principle, which can be further linked to human health, performance, and building energy consumption. This study used a novel machine learning method to automatically segment CO2 concentration time series data into build-up, equilibrium, and decay periods, and then estimated classroom ACH using the corresponding CO2 mass balance equations. This method, applied to 40 classrooms in two mechanically ventilated K-6 schools, generated up to ten ACH estimates per day per classroom. A comparison with ACH calculated using the mechanical ventilation rates with 100% outdoor air reported by the building automation system during the study period reveals a slight underestimation by the decay and build-up methods, while the equilibrium method produced closer estimates. These differences may be attributed to uncertainties in occupancy, activity, CO2 emission rates, and air mixing. This research underscores the potential of leveraging CO2 data for more comprehensive IAQ assessments and highlights the challenges associated with accurately estimating ACH in real-world settings.
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Affiliation(s)
- Bowen Du
- Human-Oriented Built Environment Lab, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Ibrahim Reda
- Département de génie civil et génie du bâtiment, Faculté de génie, Université de Sherbrooke, Sherbrooke J1K 2R1 Québec, Canada
| | - Dusan Licina
- Human-Oriented Built Environment Lab, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Costa Kapsis
- Department of Civil and Environmental Engineering, University of Waterloo, Waterloo N2L 3G1 Ontario, Canada
| | - Dahai Qi
- Département de génie civil et génie du bâtiment, Faculté de génie, Université de Sherbrooke, Sherbrooke J1K 2R1 Québec, Canada
| | - José A Candanedo
- Département de génie civil et génie du bâtiment, Faculté de génie, Université de Sherbrooke, Sherbrooke J1K 2R1 Québec, Canada
| | - Tianyuan Li
- Department of Civil and Environmental Engineering, University of Waterloo, Waterloo N2L 3G1 Ontario, Canada
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Yang S, Bekö G, Wargocki P, Zhang M, Merizak M, Nenes A, Williams J, Licina D. Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia? ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:1986-1997. [PMID: 38237915 PMCID: PMC10832055 DOI: 10.1021/acs.est.3c07659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 11/26/2023] [Accepted: 12/20/2023] [Indexed: 01/31/2024]
Abstract
Humans are the primary sources of CO2 and NH3 indoors. Their emission rates may be influenced by human physiological and psychological status. This study investigated the impact of physiological and psychological engagements on the human emissions of CO2 and NH3. In a climate chamber, we measured CO2 and NH3 emissions from participants performing physical activities (walking and running at metabolic rates of 2.5 and 5 met, respectively) and psychological stimuli (meditation and cognitive tasks). Participants' physiological responses were recorded, including the skin temperature, electrodermal activity (EDA), and heart rate, and then analyzed for their relationship with CO2 and NH3 emissions. The results showed that physiological engagement considerably elevated per-person CO2 emission rates from 19.6 (seated) to 46.9 (2.5 met) and 115.4 L/h (5 met) and NH3 emission rates from 2.7 to 5.1 and 8.3 mg/h, respectively. CO2 emissions reduced when participants stopped running, whereas NH3 emissions continued to increase owing to their distinct emission mechanisms. Psychological engagement did not significantly alter participants' emissions of CO2 and NH3. Regression analysis revealed that CO2 emissions were predominantly correlated with heart rate, whereas NH3 emissions were mainly associated with skin temperature and EDA. These findings contribute to a deeper understanding of human metabolic emissions of CO2 and NH3.
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Affiliation(s)
- Shen Yang
- Human-Oriented
Built Environment Lab, School of Architecture, Civil and Environmental
Engineering, École Polytechnique
Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Gabriel Bekö
- International
Centre for Indoor Environment and Energy, Department of Environmental
and Resource Engineering, Technical University
of Denmark, Kongens Lyngby, 2800 Copenhagen, Denmark
| | - Pawel Wargocki
- International
Centre for Indoor Environment and Energy, Department of Environmental
and Resource Engineering, Technical University
of Denmark, Kongens Lyngby, 2800 Copenhagen, Denmark
| | - Meixia Zhang
- Human-Oriented
Built Environment Lab, School of Architecture, Civil and Environmental
Engineering, École Polytechnique
Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Marouane Merizak
- Human-Oriented
Built Environment Lab, School of Architecture, Civil and Environmental
Engineering, École Polytechnique
Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Athanasios Nenes
- Laboratory
of Atmospheric Processes and Their Impacts, School of Architecture,
Civil & Environmental Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Jonathan Williams
- Max
Planck Institute for Chemistry, Hahn-Meitner Weg 1, 55128 Mainz, Germany
- Energy,
Environment and Water Research Center, The
Cyprus Institute, 2121 Nicosia, Cyprus
| | - Dusan Licina
- Human-Oriented
Built Environment Lab, School of Architecture, Civil and Environmental
Engineering, École Polytechnique
Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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