Air is an important physical-ecological environmental factor necessary for the life of all living beings, and as such, it directly affects health and quality of life. Given that the majority of air pollution is of anthropogenic origin, air quality primarily depends on man, who is obliged to protect it. Although there are different types of pollution, this research examines the microbiological quality of the air. In this research it was examined the microbiological quality of the air in closed laboratory rooms of the Microbiology Department of the Teaching Institute of Public Health of Primorje-Gorski Kotar County. Air sampling was carried out in the Laboratory for the diagnosis of respiratory and systemic infections, and at the counter of the Microbiology Department on the ground floor of the institution. In the Laboratory for the diagnosis of respiratory and systemic infections, disinfection was carried out after air sampling, after which the air was resampled to determine its success. The air was sampled on April 28, 2022 in the Laboratory for Diagnostics of Respiratory and Systemic Infections, and on April 29, 2022 at the counter of the Microbiology Department. The air was sampled with the MAS-100 device, and the SpeedyCare UV device was used for disinfection. For research purposes, 4 different nutrient media were used: TSA agar, UriSelect agar, chromogenic agar, and Sabouraud agar. After the colonies had grown, they were counted, followed by further identification of the microorganisms. The results of the research showed that a smaller number of microorganisms are present in the premises of the Laboratory for the diagnosis of respiratory and systemic infections compared to the counter of the Microbiology Department. Also, almost all bacterial species that have been identified do not pose a threat to human health, considering that most of them are normally present on the epithelium of the skin or the mucous membrane of the nose. Disinfection of the air reduced the number of bacterial colonies in the room, which confirmed the effectiveness of the disinfection device, but did not affect the reduction of the number of yeasts and molds, which indicated that the disinfection device is not a means intended to suppress this type of microorganisms.