Risk assessment on bioaerosols deposition in classrooms

Pao Yue-kong Library Electronic Theses Database

Risk assessment on bioaerosols deposition in classrooms


Author: Lau, Pui Shan
Title: Risk assessment on bioaerosols deposition in classrooms
Degree: M.Eng.
Year: 2012
Subject: Schools -- Health aspects.
Airborne infection.
Communicable diseases -- Transmission.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: viii, 91 leaves : ill. (chiefly col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2525557
URI: http://theses.lib.polyu.edu.hk/handle/200/6641
Abstract: Most children spent much of their childhood in schools. However, due to the presence of many students in a classroom of limited space, students may easily get infected by the transmission of airborne pathogen. Better understanding of airborne bioaerosols transmission in classrooms is crucial in improving exposure assessments in schools. However, limited study on risk assessment of bioaerosols deposition in classrooms can be found. This study aims to examine the transport characteristics of bioaerosols and the susceptible area due to coughing of a student inside a typical classroom. Both experimental approach and computational modeling were adopted to investigate the transport mechanism of particles under various airflow velocities and diffuser arrangement. Area which is susceptible to high exposure of particles under different fan coil unit velocity settings, orientation of bioaerosols generation source and various shape of particles are also examined. Moreover, predominant particle size in typical classroom and the corresponding infection area are explained. Inferring from the computational simulation results, the high risk infection area due to coughing was as far as 3.5 metre away from the particle generation source even under low airflow velocity. Under high velocity settings, the high risk infection areas are even sufficiently large enough to cover entire small classroom. Moreover, high velocity airflow induced great turbulence to the particle movement, causing the dispersion and deposition of particles become more unpredictable. When the student is coughing sideward, the particles can travel to almost entire classroom, which is undesirable. This can be explained by the turbulent airflow. Sideward injections of particles fall into the turbulence airflow field soon, resulting in a wide coverage area. In the meantime, the bioaerosol are commonly found to be composed of spherical and non-spherical shape. The simulation results reveal that the general transport characteristics do not affect much when the particles are non-spherical. Generally, it is found that the portion of turbulence airflow increases with the airflow velocities, which lead to a wider coverage area of injected particles stream in a classroom. This implies that more attended students are exposed to virus-laden airborne pathogens under higher airflow velocity. This study extends the current understanding of risk assessment on bioaerosols in a typical classroom.

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