Summary During bronchoscopy examinations performed in hospitals, aerosols coming from the patient’s mouth and nose can be found suspended in the ambient air. The aerosols produced may contain pathogenic microorganisms such as mycobacteria, viruses, and even moulds. These microorganisms can also be aerosolized during bronchoscope cleaning after the examinations. Depending on the nature of the microorganisms or bioaerosols, they can remain in the air for a relatively long time and potentially cause infections in exposed workers. The main aim of this study was to measure the sizes and concentrations of the biological and non-biological particles present during bronchoscopy examinations and bronchoscope reprocessing, and to propose preventive or corrective measures if need be. Two bronchoscopy rooms and one reprocessing room were studied. One of the two bronchoscopy rooms did not meet the recommendations of the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) or of the American Institute of Architects (AIA). A TSI 3314 ultraviolet aerodynamic particle sizer (UV-APS) was used to establish the concentrations and fine structures of the non-fluorescent and fluorescent particles present, in real time, before, during, and after the bronchoscopy examinations. This instrument measures the aerodynamic diameter of the aerosols and can distinguish the original biological fraction in real time. Reference concentrations were measured before the start of the examinations (initial background noise) and used as levels of comparison for the concentrations measured during and at the end of the bronchoscopies. The results obtained with the UV-APS were compared to those obtained using other microorganism sampling methods, by impaction in a liquid using an AGI-30 impinger and a Coriolis sampler, and directly on agar using an Andersen impactor. These samples were analyzed using agar culture methods, and for samples in a liquid medium, using molecular biology methods. Simultaneously with the bioaerosol evaluations (concentration, identification, suspension time, and particle size) in real situations, computational fluid dynamics (CFD) made it possible to isolate and understand various factors that can affect contamination levels in bronchoscopy rooms. The concentrations of the non-fluorescent and fluorescent particles (bioaerosols) were significantly higher (p≤0.05) than the reference concentrations (morning background noise) during the bronchoscopy examinations. For the studied factors, the bioaerosol concentrations were significantly higher during bronchoscope insertion tasks and then during the bronchoscopy examination. Some of the opportunistic pathogenic aerosols classified in risk group 2 (e.g. Streptococcus pneumoniae) likely came from the patient and not the caregiving personnel. The bioaerosol concentrations during the cleaning operations performed in the reprocessing room were not significantly higher than the reference concentrations. The time required at the end of the day for the bioaerosols to reach the morning reference concentrations was about 15 minutes for both bronchoscopy rooms. Our models based on computational fluid dynamics (CFD) enabled us to observe bioaerosol behaviour in the two bronchoscopy rooms.