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 instrume nt for separately monitoring ambient aerosol concentrations of biological a nd nonbiological composition. A method of outdoor testing, and recent resul ts, are also described. The single-particle fluorescence analyzer (SPFA) dr aws ambient air into an optical chamber through a sampling nozzle. Detectio n signals from each aerosol particle consist of an elastic scattering respo nse as well as fluorescent emission in two distinct spectral bands. Differe ntiation of biological aerosols is based on the relative intensity of ultra violet (UV) fluorescence measured from the particles following excitation w ith a 266-nm-wavelength laser pulse. During outdoor tests two types of orga nisms were released as aerosol sprays: Erwinia herbicola vegetative cells a nd Bacillus subtilis spores. The SPFA participated in 39 of a total set of 40 outdoor tests. Twenty-seven tests released E. herbicola and nine release d B. subtilis. Analysis of these results indicates that a reliability of de tection of about 90% for E. herbicola, and of about 87% for a. subtilis wer e achieved under the conditions of the tests, with a sensitivity near 1 par ticle/l, Some tests involved release of nonbiological aerosols that did not result in a significant change in fluorescent signals in the instrument. ( C) 1999 John Wiley & Sons, Inc.*