The purpose of this study was to determine the amount of particulate and microbial contaminants, i.e. bacteria and fungi found in indoor air in a lecture hall in one of Lublin's universities and their classification. In the research part, the amount of particulate and microbial pollutants was measured. Bioaerosols were investigated using an Andersen cascade impactor, which was located in the central part of the room at a height of 1-1.5 m, and single-level impactors. Identification of the microorganisms present in indoor air was carried out. The air in the room was sampled before the start of class to determine the "background," i.e. the concentration level of microbial contaminants in the classroom without the presence of students. Subsequent measurements were taken during teaching activities in the presence of students and the teacher. The study shows that the air condition in the classroom during its operation met the requirements in terms of PM2.5, PM10 and microorganisms. The highest risk was recorded for carbon dioxide. Moreover, the highest recorded readings of this pollutant coincided with the maximum concentrations of the other monitored quantities. Therefore, it can be unequivocally stated that in the case of the analyzed room, monitoring carbon dioxide and adjusting the size of the ventilation airflow to maintain its concentration within the limit of 1000 ppm would guarantee the maintenance of adequate indoor air quality. The study showed no correlation between CO2 concentration and measured concentrations of microbial contaminants.