NOVELTY - An aerosol fluorescence spectrum analyzer (AFSA) comprising a pulsed laser and photosensor triggered by logically ANDed trigger lasers/detectors detecting particles in the sample flow, is new.    USE - The apparatus and method are useful for fluorescence probing of particles flowing in a fluid (claimed), particularly for detecting airborne microorganisms (bioaerosols) or other single airborne particles. The apparatus is disclosed as being potentially useful for monitoring bioaerosols associated with air handling systems, dairy operations or other operations involving animals, sewage processing and sludge usage, and also for detection of biowarfare agents.    ADVANTAGE - The novel AFSA is capable of reliable and rapid (real time) fluorescence spectrum detection, particle sizing (even for particles as small as 2 microm diameter), analysis, and classification of biological aerosols. Minority biological particles can be detected in the presence of much larger numbers of nonbiological particles.    DETAILED DESCRIPTION - An aerosol fluorescence spectrum analyzer (AFSA) comprises a triggerable pulsed laser for fluorescent probing of a particle, and optical means for collecting fluorescence emitted from the particle, and for focusing it in a detection region, where the signal is detected by a spectral detector. The analyzer further comprises first and second triggering lasers for directing and focusing two approximately orthogonal beams of wavelength lambda1 and lambda2 on a trigger volume, and corresponding first and second wavelength-selective detectors which provide output signals upon detection of scattered light of wavelength lambda1 and lambda2 respectively. The output signals are ANDed and gate the spectral detector which detects fluorescence signals emitted from a particle being probed by the triggerable pulsed laser while the laser is in the ON state.    An INDEPENDENT CLAIM is also included for fluorescence probing particles flowing in a fluid comprising:    (a) defining a trigger volume in the fluid by intersecting a plurality of intersecting orthogonally aimed trigger laser beams each of different wavelength;    (b) detecting light scattered from the vicinity of the trigger volume by a plurality of wavelength-selective detectors matched to the wavelengths of the trigger beams;    (c) probing a detected particle with a pulsed laser light triggered by the particle detectors; and    (d) collecting fluorescence emitted from a particle in a detection volume and focusing it in a detection region.    DESCRIPTION OF DRAWING(S) - The figure shows a top view schematic diagram of an aerosol fluorescence spectrum analyzer as above.    Detection volume (20)    Q-switched UV laser (90)    PMT tubes (40, 50)    Single channel analyzers (60, 70)    AND gate (80)    Intensified CCD controller (95)    Intensified CCD camera (96)    Spectrograph (97)    Long pass filter (98)    Reflecting objective (30)    Computer (100)