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ADVANCING KNOWLEDGE OF INDOOR AEROSOL SOURCES, FATE, TRANSPORT, AND CONTROL
Title
ADVANCING KNOWLEDGE OF INDOOR AEROSOL SOURCES, FATE, TRANSPORT, AND CONTROL
Creator
Azimi, Parham
Date
2016, 2016-12
Description
Recent evidence suggests that particulate matter (of both indoor and outdoor origin) is one of the most important airborne pollutants driving...
Show moreRecent evidence suggests that particulate matter (of both indoor and outdoor origin) is one of the most important airborne pollutants driving adverse health effects worldwide. Despite our understanding of major indoor aerosol sources that contribute to adverse health effects across the population, gaps in our knowledge of some aspects of the sources, fate, transport, and control of indoor aerosols still remain. This dissertation focuses on filling three major gaps related to indoor aerosols. The first objective of this dissertation is to improve knowledge of the impacts of particle filtration in central heating, ventilation, and air-conditioning (HVAC) systems on fine particles smaller than 2.5 μm in diameter (i.e., PM2.5) and ultrafine particles smaller than 100 nm in diameter (i.e., UFPs) of outdoor origin that penetrate into the indoor environment. Results demonstrate that higher-efficiency HVAC filters can significantly reduce indoor proportions of outdoor PM2.5 and UFPs inside residences, but home vintage, climate zone, and ventilation strategy strongly influence the outcomes due to widely varying air exchange rates, HVAC system runtimes, and sources of ventilation air. The second objective of this dissertation is to improve knowledge of emissions and control of particulate matter from a recently established source of indoor pollutants: desktop three-dimensional (3D) printers. Median estimates of time-varying UFP emission rates ranged from ~108 to ~1011 #/min across all tested combinations, varying primarily by filament material and, to a lesser extent, bed temperature. It was also shown that UFP concentrations within close or moderate proximity to some desktop 3D printer and filament combinations can exceed recommended exposure levels. The most effective control strategies for reducing pollutant concentrations emitted from desktop 3D printers wereinstalling a high-flow spot ventilation system and operating the printer in a sealed enclosure with high efficiency gas and particle filtration. Finally, the third objective of this dissertation is to improve knowledge of the fate, transport, and control of infectious diseases in indoor environments through mathematical modeling of bioaerosol transmission and infection risk. Results demonstrate that Recirculating HVAC filtration can achieve risk reductions at lower costs of operation than equivalent levels of outdoor air ventilation, particularly for MERV 13-16 filters. It was also shown that in addition to the biological characteristics of respiratory pathogens, human activities, interzonal airflows, and physical properties of bioaerosols can substantially impact the infection transmission risk. Further, the dominant pathway for influenza transmission indoors under most conditions was airborne transmission. Finally, estimations of the back-calculated quanta generation rate for influenza viruses were directly in line with the existing data gathered from prior epidemiology studies.
Ph.D. in Environmental Engineering, December 2016
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