Abstract: The invention provides a bacteria detection system for continuous monitoring of the concentration of pathogenic bio-logical particles: bacteria and viruses, their fragments, and other particles suspended in ambient air. The optical structure of the system includes airflow channel (1) with inlet and outlet units, excitation channel (4) with excitation unit and sensor channel (7) with sensor unit. The airflow channel is a long tube with two sections, first section and the second section, wherein between longitudinal axis of the first section and the longitudinal axis of the second section is an angle ?. The detectable particle flows through the air flow channel and is radiated from the excitation channel, generating a fluorescence signal that enters the sensor channel (7) and the sensor unit (9). The operating mode of the device is controlled by the controller combined with the processor (81).