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Review and Extension of CO2-Based Methods to Determine Ventilation Rates with Application to School Classrooms

Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, MI 48109, USA
Academic Editors: Alessandra Cincinelli and Tania Martellini
Int. J. Environ. Res. Public Health 2017, 14(2), 145;
Received: 23 December 2016 / Revised: 25 January 2017 / Accepted: 28 January 2017 / Published: 4 February 2017
(This article belongs to the Special Issue Indoor Air Quality and Health 2016)
PDF [1202 KB, uploaded 4 February 2017]


The ventilation rate (VR) is a key parameter affecting indoor environmental quality (IEQ) and the energy consumption of buildings. This paper reviews the use of CO2 as a “natural” tracer gas for estimating VRs, focusing on applications in school classrooms. It provides details and guidance for the steady-state, build-up, decay and transient mass balance methods. An extension to the build-up method and an analysis of the post-exercise recovery period that can increase CO2 generation rates are presented. Measurements in four mechanically-ventilated school buildings demonstrate the methods and highlight issues affecting their applicability. VRs during the school day fell below recommended minimum levels, and VRs during evening and early morning were on the order of 0.1 h−1, reflecting shutdown of the ventilation systems. The transient mass balance method was the most flexible and advantageous method given the low air change rates and dynamic occupancy patterns observed in the classrooms. While the extension to the build-up method improved stability and consistency, the accuracy of this and the steady-state method may be limited. Decay-based methods did not reflect the VR during the school day due to heating, ventilation and air conditioning (HVAC) system shutdown. Since the number of occupants in classrooms changes over the day, the VR expressed on a per person basis (e.g., L·s−1·person−1) depends on the occupancy metric. If occupancy measurements can be obtained, then the transient mass balance method likely will provide the most consistent and accurate results among the CO2-based methods. Improved VR measurements can benefit many applications, including research examining the linkage between ventilation and health. View Full-Text
Keywords: ventilation; air change rate; carbon dioxide (CO2); schools; classrooms; indoor air quality ventilation; air change rate; carbon dioxide (CO2); schools; classrooms; indoor air quality

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Batterman, S. Review and Extension of CO2-Based Methods to Determine Ventilation Rates with Application to School Classrooms. Int. J. Environ. Res. Public Health 2017, 14, 145.

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