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Indoor air quality (IAQ) is crucial for the health, well-being, and productivity of office occupants. IAQ is strongly influenced by occupancy and the operational mode of the heating, ventilation, and air conditioning (HVAC) system. This study investigates the spatiotemporal variations in ozone (O3) and carbon dioxide (CO2) concentrations throughout the HVAC system of a LEED-certified office building. A four-month field measurement campaign was conducted at the Ray W. Herrick Laboratories, employing an automated multi-point sampling system to monitor O3 and CO2 at eight locations throughout the HVAC system. The objectives of this study are to characterize the spatiotemporal distribution of these gases under different ventilation modes and occupancy levels, and to identify O3 loss mechanisms in the office and its HVAC system. Spatiotemporal variations in O3 and CO2 concentrations were observed throughout the HVAC system. Results indicate that outdoor air exchange rates (AERs) significantly impact indoor O3 levels, with higher AERs resulting in increased indoor O3 but reduced CO2 concentrations. Measurements reveal that HVAC filters and ducts contribute to O3 loss, with up to 18% O3 removal observed in the longest HVAC duct segment. Additionally, occupancy influences O3 deposition onto human skin and clothing surfaces. This research underscores the limitations of ventilation standards that focus only on CO2, highlighting the need for ventilation strategies that consider the effects of occupancy and outdoor AERs on different gases. By integrating multi-point gas sampling into building automation systems, more effective control strategies can be developed to enhance IAQ and occupant health while reducing energy consumption.
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A longitudinal study of IAQ metrics and the efficacy of default HVAC ventilation
People spend approximately 90% of their time indoors, making effective indoor air quality (IAQ) monitoring crucial for occupants’ well-being. Traditional IAQ monitoring primarily focuses on carbon dioxide ( ) levels to inform the operation of Heating, Ventilation, and Air Conditioning (HVAC) systems. However, HVAC systems often overlook other critical IAQ metrics, such as volatile organic compounds (VOC), which may correspond better to occupant activities in some cases. This naturalistic study, conducted over four months at the University of Virginia, addresses this significant gap by observing changes in VOC and levels across various times, events, and spaces, including conference rooms, single occupancy offices, and common open-space areas. We aimed to determine whether can be the only representative of IAQ for dynamically adjusting the ventilation rates within this testbed. A key focus was on poor IAQ instances where levels were below the recommended levels, but VOC concentrations exceeded them, potentially impacting occupants’ health and well-being. Our results revealed that in the studied conference room, poor IAQ conditions prevailed 71% of the time during occupancy, in contrast to lower rates in single occupancy offices (11%, 7%, and 16%). Notably, while social events influenced levels less, VOC levels significantly increased in all open-space areas. These findings challenge the conventional reliance on monitoring for IAQ management, highlighting the necessity of incorporating comprehensive IAQ metrics in HVAC systems. The study underscores the critical need for dynamic HVAC systems that adapt to real-time IAQ conditions, a vital step towards enhancing indoor environmental quality in various settings.
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- Award ID(s):
- 2326408
- PAR ID:
- 10553422
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Building and Environment
- Volume:
- 254
- Issue:
- C
- ISSN:
- 0360-1323
- Page Range / eLocation ID:
- 111353
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.buildenv.2024.111353
