Date of Award

3-24-2026

Thesis Type

PhD

Document Type

Thesis

Divisions

Faculty of Built Environment

Department

Department of Building Surveying

Institution

Universiti Malaya

Abstract

Airborne diseases pose a serious public health threat, particularly in street stores characterized by frequent but short-duration customer visits. Unlike larger buildings, these small commercial spaces exhibit fluctuating and unpredictable occupancy patterns, creating unique virus transmission dynamics. However, research on infection risks and ventilation strategies for such environments remains limited. In bridging this gap, customer traffic and ventilation conditions were monitored in 31 individuals street stores in Baotou, China (April–May 2023), identifying critical influences of building characteristics, occupancy patterns on transmission risks, and defining the typical street store. Within a representative store, CO₂ decay tracer gas experiments (May 2024) and computational fluid dynamics (CFD) simulations using the RNG k–ε RANS model were conducted to analyze virus dispersion characteristics and airflow patterns under various fan configurations, with infection risks quantified using the Wells-Riley model. Subsequently, 17 case simulations were performed employing the Response Surface Methodology (RSM) and CFD under two optimal ventilation setups: natural ventilation. The findings demonstrate that ventilation design in street stores must simultaneously consider airflow patterns and occupant behavior. Both NV+CF-3 and EXF2600 configuration effectively expelled viral particles from occupants' breathing zones, maintained high virus removal efficiency without spreading contaminants extensively. Although transient customer movements marginally reduced the performance of NV+CF-3 and EXF2600 configurations, the overall effect remained insignificant. Upward rotating ceiling fans combined with NV initially demonstrated potential to reduce indoor infection risks. However, the resulting airflow patterns promoted the transport and wider dispersion of virus-laden particles, indicating that this ventilation strategy may increase transmission risk. Elevated infection risks near EXFs indicate that occupant positioning is critical; therefore, employees are advised to position themselves away from store entrances. Incorporating a desk fan oriented toward the outlet (DFout) near employee areas may function as a temporary mitigation strategy, helping to reduce the intrusion of viral particles. Time management proved critical: implementing a two-minute interval between customer visits substantially lowered residual viral particle concentrations. Additionally, as for the extended prediction analysis across all street stores, the results identified floor area, fan speed, and background ventilation as key determinants for CFs, with notable interaction effects between fan speed and ventilation conditions. For EXFs, floor area, fan size, and installation location significantly influenced infection risk. Larger fans were more effective in smaller spaces but yielded diminishing returns in larger rooms. Overall, optimal infection control depended on the coordinated configuration of multiple variables rather than any single factor, and RSM successfully identified parameter ranges that minimize infection risk. Overall, this study establishes an integrated framework for evaluating and optimizing fan-assisted ventilation strategies in street stores and provides practical guidance for infection risk mitigation in compact commercial environments.

Initial

khm

Additional Information

Thesis (PhD) – Faculty of Built Environment, Universiti Malaya, 2026.

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