REAL-TIME EVALUATION OF VOLATILE CHEMICAL EMISSIONS AND EXPOSURES DURING DISINFECTION PROCESSES IN BUILDINGS
Creators: name: Ding, Xiaosu
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 330206
subject: Building science, technologies and systems

description: People spend approximately 90% of their time indoors, where they are exposed to a wide variety of particle- and gas-phase air pollutants. The COVID-19 pandemic has intensified the chemical disinfection of high-touch surfaces in occupational workplaces and residential buildings. The use of chemical disinfectants may introduce more pollutants into the indoor environment. These intensive disinfection activities may lead to high human exposure to the released VOC mixtures and potentially adverse effects on the health of disinfection workers and occupants. Thus, it is critical to characterize the VOC mixtures and estimate human exposure during the building disinfection events with various disinfectant products and different disinfection cases and exposure scenarios. This dissertation aims to (1.) evaluate and characterize the VOC emissions during the building disinfections; (2.) assess the low-cost sensor performance to measure VOCs via the PTR-TOF-MS during building disinfections; (3.) compare the VOC measurements and human exposure between breathing zone and bulk air experiment setups; (4.) evaluate the impact of indoor emissions on human exposure during different usage cases of building disinfection.To achieve these objectives, this thesis presents three studies based on a field experiment campaign conducted at the Purdue Zero Energy Design Guidance for Engineer (zEDGE) Tiny House in the fall of 2020. First, this thesis presents a study to evaluate the real-time performance of PID in sensing indoor VOC mixtures during building disinfection events through co-location measurements with a PTR-TOF-MS during spray-based disinfectants. The measurements demonstrated that the PID was successful in identifying VOC emission events during the application of the disinfectants. Thus, PIDs may be suitable for integration with building automation systems for ventilation control. The PID response was less than the PTR-TOF-MS response, suggesting that the PID could more efficiently detect many components of the emitted VOC mixtures. Detailed correlation analysis between the PID and PTR-TOF-MS responses provides a basis for improving the reliability of PIDs in estimating VOC concentrations through the application of product-specific correction factors.Secondly, this thesis conducts an experimental case study to demonstrate the application of PTR-TOF-MS for mobile breathing zone (BZ) monitoring of VOCs in workplace environments during disinfection activities. Worker inhalation exposure to VOCs was evaluated by attaching the PTR-TOF-MS sampling line to the researcher’s BZ while the disinfection activity was carried out throughout the building. The results show significant spatiotemporal variations in VOC concentrations can occur in the worker’s BZ during multi-surface disinfection events. The application of high-resolution monitoring techniques, such as PTR-TOF-MS, is needed to advance the characterization of worker exposures and develop appropriate mitigation strategies for volatile disinfectant chemicals.<br>Lastly, this thesis provides a comprehensive evaluation study on human exposure to VOCs during PAA-based building disinfection events via real-time measurement and disinfection event modeling. The results revealed that PAA-based surface disinfection can lead to an excessive increase in PAA concentrations. BZ experiments demonstrated a spatiotemporal variation in PAA concentrations. The missing mass inhaled measured by the PAA monitor indicated that the human inhalation exposure identified by BZ experiments may be much higher than in bulk air (BA) experiments; thus, a mobile measurement in their breathing zones can better understand the occupants’ exposure to PAA during a building disinfection event. The disinfection event modeling indicated that PAA-based building disinfection may lead to excessive human exposure when using high dilution ratios and/or turning off mechanical ventilation. Such exposure could potentially leave a severe or even irreversible effect on occupant health. These findings suggested that a disinfection protection plan/protocol is necessary for workers, ensuring a required dilution for a disinfectant solution and enough ventilation rate for a safe PAA disinfection event. For the general public who may have difficulties developing professional disinfection procedures, pre-diluted disinfection products with a warning of turning on ventilation could be a more suitable alternative for PAA-based disinfection.