Real-time measurement of bacterial aerosols with the UVAPS: performance evaluation

The Ultraviolet Aerodynamic Particle Sizer (UVAPS, Model 3312, TSI Inc., St. Paul, MN) spectrometer is the only commercially available aerosol counter for real-time monitoring of viable bioaerosols. Though the feasibility of this technique to monitor bioaerosols has been previously demonstrated by the instrument designers in a number of studies, the collection of meaningful data and their correct interpretation are still not possible without a thorough understanding of its capabilities and limitations. This paper presents the results of the first independent study aimed towards evaluating selectivity, sensitivity, counting efficiency, and the detection limits of the UVAPS. The study has demonstrated limitations in the capability of the instrument to measure bacterial spores that is explained by biochemical composition of the spores, which contain only minute amounts of the specific fluorophores that appeared to be below the instrument sensitivity level. The results were also indicative of strong sensitivity of the UVAPS to the physiological state of bacteria. Counting efficiency of the fluorescent particles was shown to depend on particle concentration with the upper limit of detection of the UVAPS around 6 x 107 particles/ m3.

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