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Environmental polydisperse bioaerosol measurements in classrooms with and without Upper-Room Ultraviolet Germicidal Irradiation
Abstract
Upper-Room Ultraviolet Germicidal Irradiation (UVGI) is known to inactivate bioaerosols in laboratory and chamber environments. This study was developed to begin filling the current knowledge gap between theoretical researches in laboratory and field application. The primary objective is to develop a constructional protocol for evaluating the effect of upper-room UVGI on polydisperse bioaerosols in classroom settings and find the key factors that influence the concentration of bioaerosols in classrooms at the field. A literature review was first summarized about laboratory and field evaluations of upper-room UVGI. The review explored currently available ways of measuring bioaerosols. Cultural method by impactors and continuous monitoring of bioaerosols by fluorescent signals were chose. Each sampling method operated with designed sampling procedures. Bioaerosols samples by two sampling methods have shown fine size (0.5 µm-3µm) and total bioaerosols in the UVGI classroom were statistically significant lower than the non-UVGI classroom in 12 of the 20 visiting days. A significantly higher level of bioaerosols during the occupied periods than unoccupied ones was found in every visiting day. A new parameter, fraction of fluorescent bioaerosols to total aerosols, has proven to be a good indication in reflecting the occupancy status for indoor environments. More than 60% of the visiting days had lower concentrations of 0.5 µm bioaerosols in the UVGI classroom during the following crossover measurement. This number dropped to or less than 50% when grouped with larger channels of bioaerosols. An analytical model was developed to simulate decay process of polydisperse bioaerosols in classroom. The results from both the model and measurement indicated that total and small size of fluorescent bioaerosols decayed faster comparing to same size aerosols. The decay rate by UVGI played a significant role for bioaerosols at 0.5 µm. When the susceptibility of airborne microorganisms to UVGI is higher, the decay rate by UVGI improves from 0.3/hour to 34/hour. The simulation of decay rates in classrooms helps to interpret the potential effects of ventilation, UVGI, and other factors on bioaerosols. The results indicate that upper-room UVGI could be an effective method to disinfect airborne microorganisms - especially when the size of the bioaerosols is 0.5 µm.
Subject Area
Microbiology|Architectural engineering|Environmental Health|Environmental Studies
Recommended Citation
Su, Chunxiao, "Environmental polydisperse bioaerosol measurements in classrooms with and without Upper-Room Ultraviolet Germicidal Irradiation" (2014). ETD collection for University of Nebraska-Lincoln. AAI3667018.
https://digitalcommons.unl.edu/dissertations/AAI3667018