## 1 Introduction  
The term \"bio-aerosol\" is used to describe various substances: microorganisms and their fragments, toxins, and particles originating from the decay of various living organisms. Bio-aerosol may contain live bacteria and their spores, viruses, fungi, leaf fragments, pollen, cellulose, humic and fulvic acids, chlorophyll, and dust [1]. In addition, aromatic hydrocarbons from industrial and engine exhaust appear in the air. We inhale and exhale air containing many such particles, which may affect human health [2, 3]. Air monitoring has become an important element of civil protection. In addition to civilian applications for testing air purity in workspaces, public utilities, and residents, an early warning system against a potential bioterrorist activity is used. Of the thousands of bacteria, only a small percentage cause infection and disease [4]. However, only 45 are considered by CDC as potential bio-weapons [5]. The laser-induced fluorescence (LIF) method is used to build sensitive analyzers of biological agents in both civilian and military applications. This method is used for the detection and classification of biological material in water [6], in the air [7, 8, 9, 10, 11, 12, 13], and on the surface [14, 15, 16]. Fluorescence is the most sensitive spectroscopic method, and it has been used in many fields of research, including medicine [17, 18, 19]. The LIF methods are mainly based on the analysis of one or two emission bands. It has been shown that the fluorescence of a single particle excited with more than one wavelength can strongly improve the classification of bio-aerosols due to the involvement of emission from various fluorophores. The fluorescence spectra do not provide sufficient information for clear and reliable identification of air-borne species but allow rough, real-time discrimination of naturally or intentionally released biological warfare agents from interferents [20; 21; 22]. An important parameter of fluorescence, apart from spectra, is the fluorescence lifetime. Steady-state fluorescence spectra indicate that the emission phenomenon occurs at specific wavelengths of radiation, while the fluorescence lifetime indicates how this phenomenon occurs. The fluorescence lifetime of bio-fluorophores is very sensitive to their microenvironment in the protein and makes it possible to discriminate between different biological molecules. The research aims to conduct a systematic study to create a lifetime domain database of dry biological samples for real-time detection and monitoring systems. Some reports on the time-resolved fluorescence of microorganisms were published. Usually, one or two decay time models have been applied to describe the decay kinetics of the samples [23; 24; 25; 26]. [PERSON] and [PERSON] used a stroboscopic technique for fluorescence decay analysis of albumin and found at least three lifetime components [27]. This article presents the basics of the method, the construction of the equipment, and techniques used for the measurement of fluorescence lifetimes. The aim of the current work was to determine a database of fluorescence lifetimes of biological substances that are simulants and interfereants of biological warfare agents (BWAs). In addition to vegetative bacteria, their spore forms, plant pollen and fungi, and commercial bioinsecticides used in agriculture were also examined. At the Institute of Optoelectronics (IOE), many devices for BWA detection have been developed and implemented [13; 28], including fluorescence lidars [9]. The developed database is the basis for the IOE engineers to build more advanced LIF analyzers based on a combination of spectra and fluorescence lifetime measurements, which allows improved classification selectivity. A common, recommended method for testing lifetimes is Time-Correlated Single Photon Counting (TCSPC) [29]. For the analysis of small concentrations of biological substances, the method has many limitations.