Background and Purpose: Hospital air contains bioaerosols that are potential infection sources for patients and staff. This study focused on identifying and quantifying bacterial bioaerosols in Montaserieh Hospital, Mashhad, in 2021.

Materials and Methods: This cross-sectional analytical study collected 96 air samples from operating rooms and wards using a sampling pump with a flow rate of 28.3 L/min and a single-stage Anderson impactor by NIOSH0800 guidelines. The samples were cultured, and bacterial colonies were quantified as colony-forming units per cubic meter (cfu/m³). Data analysis was performed using SPSS software.

Results: Predominant bacterial bioaerosols identified included Micrococcus lotus, Coccoriacristina, and Staphylococcus hominis. The mean density of bioaerosols was 57.81 cfu/m³ (standard deviation = 42.44), aligning with World Health Organization guidelines. The intensive care unit exhibited the highest average density at 101.08 cfu/m³ (standard deviation = 48.93), whereas the bone marrow transplant ward had the lowest at 5.25 cfu/m³ (standard deviation = 7.96). 

Conclusion: The study revealed varying densities of bacterial bioaerosols across different hospital wards, though the types of bacteria were consistent. Variations in bioaerosol density likely relate to the number of patients and staff per room, the quality of ventilation, and environmental sanitation standards.
 
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