Detection of bioaerosols using multiwavelength UV fluorescence spectroscopy

This article describes the development of an aerosol generation apparatus t o investigate the fluorescence spectra of bioaerosols, The experimental sys tem was set up in a Biosafety Level II Laboratory, The system included an a erosol generator, chamber, aerosol monitoring instrumentation, and laser-in duced-fluorescence detection system. The aerosol generators, chamber, and m onitors were housed in an enclosure with the exhaust vented through a doubl e HEPA filtration system. A Hospitak nebulizer using aqueous suspensions ge nerated aerosols of bacteria. Aerosols of pollens mere generated using a sm all-scale dry powder generator. The aerosol chamber, with four windows for optical access, was designed with the aid of a computational fluid dynamics code to optimize the generation of aerosol beams with a well-defined geome try for reproducible fluorescence measurements. Aerosol concentrations and aerodynamic diameters in the chamber were determined using a biter, an impi nger, a modified Andersen impactor, and an Aerodynamic Particle Sizer. Geom etric size and particle shapes were determined using microscopy and imaging analysis. The well-characterized aerosol stream allowed reproducible fluor escence measurements to be made with the aerosol generation methods develop ed in this work. Fluorescence spectra of four bacteria, Escherichia coli, S taphylococcus aureus, Bacillus subtilis var niger, and Bacillus thuringiens is, were found to be very similar. Calibrations of the fluorescence instrum entation allowed cross sections of live cells, killed cells, and spores to be measured with an uncertainty of about 2 to 5.