An optical detecting technique to identify bio-aerosol particles is proposed in this paper by normalized fluorescence
value which correlates to its size and intrinsic fluorescence. With the bio-aerosol detecting system developed, we test and
analyze three types of aerosols, while each of them contains fluorescent microspheres of a certain size. The result
indicates that different fluorescent microspheres containing the same fluorescent substances have the same normalized
fluorescence voltage to unit particle size in diameter. The normalized fluorescence value of other species aerosols is
tested for comparing. The research results can be applied to identification of bio-aerosols preliminarily.
Based on the measurement of intrinsic fluorescence, a set of bio-aerosol including virus aerosols detection
instrument is developed, with which a method of calibration is proposed using tryptophan as the target. The
experimental results show a good linear relationship between the fluorescence voltage of the instrument and the
concentration of the tryptophan aerosol. An excellent correlation (R<sup>2</sup>≥0.99) with the sensitivity of 4000PPL is
obtained. The research demonstrates the reliability of the bio-aerosol detection by measuring the content of
tryptophan. Further more the feasibility of prejudgment to the species of bio-aerosol particles with the multi-channel
fluorescence detection technology is discussed.