Continuous, rapid biological aerosol detection with the use of UV fluorescence: Outdoor test results

This report describes the design and principles of operation of an instrument for separately monitoring ambient aerosol concentrations of biological and nonbiological composition. A method of outdoor testing, and recent results, are also described. The single-particle fluorescence analyzer (SPFA) draws ambient air into an optical chamber through a sampling nozzle. Detection signals from each aerosol particle consist of an elastic scattering response as well as fluorescent emission in two distinct spectral bands. Differentiation of biological aerosols is based on the relative intensity of ultraviolet (UV) fluorescence measured from the particles following excitation with a 266-nm-wavelength laser pulse. During outdoor tests two types of organisms were released as aerosol sprays: Erwinia herbicola vegetative cells and Bacillus subtilis spores. The SPFA participated in 39 of a total set of 40 outdoor tests. Twenty-seven tests released E. herbicola and nine released B. subtilis. Analysis of these results indicates that a reliability of detection of about 90% for E. herbicola, and of about 87% for B. subtilis were achieved under the conditions of the tests, with a sensitivity near 1 particle/l. Some tests involved release of nonbiological aerosols that did not result in a significant change in fluorescent signals in the instrument. © 1999 John Wiley & Sons, Inc.* Field Analyt Chem Technol 3: 249–259, 1999