| Summary: | 碩士 === 國立臺灣大學 === 職業醫學與工業衛生研究所 === 102 === he survival characteristics of bioaerosols needed to be considered because they influenced the effectiveness of infection. The survivability of bioaerosols was found to depend on a number of interacting factors, and was not easy to predict. Although there have been many publications on the effect of environmental factors on the survivability of airborne infectious organisms, the results were difficult to compare. Therefore, this work aimed to establish a robust approach to characterizing the survivability of bioaerosols.
In the present study, an inkjet system was employed to generate monodisperse aerosols. Potassium sodium tartrate solution and suspensions of polystyrene latex and yeast were used as test agent. An appropriate driving signal, i.e., a square wave with voltage 14 -18 V and pulse width 14 - 20 μs under frequency 3000 Hz, was used to squeeze the suspension out of a 50-μm nozzle. A high resolution camera was used to monitor and assure that the droplets were uniform in size. Dispersion air was required to reduce droplet coagulation, especially under high generation frequency. The droplets were introduced into a 3-m vertical chamber (diameter 20 cm) to investigate the effect of relative humidity and airborne time on yeast survivability. An aerodynamic particle sizer was used to monitor the size distribution and number concentration of aerosol particles coming out the inkjet generator. A Marple cascade impactor, a SKC bio-sampler, and gelatin filters were used to sample the challenging yeast particles.
The results showed that using inkjet printing method to generate bioaerosols was feasible. The generated droplets were ideally 50 μm with a GSD of 1.06. The optimal concentration of suspension to form droplets was about 4.6×106 #/ml. The fractions of droplets with particle to total droplets, and droplets with one particle to all droplets with particles were about 0.26 and 0.86, respectively. Viability test results showed no significant difference between low humidity (20%) and high humidity (86%). Airborne time up to 39 min under the dried condition of RH 20% did not affect the yeast viability, showing that yeast is resistant to low humidity environmental. However, the viability data from different sampling methods were significantly different: impactor 10%, gelatin filter 15%, and impinger 65%. Accordingly, the bioaerosol sampling methods were more influential on the viability of microorganisms.
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