Introduction:
The quality of indoor air is one of the most important factors affecting health and well-being of people, who inhale 10m³ of air every day and spend 80–95% of life indoors. The aim of this research was to evaluate the occurrence of airborne fungi, along with assessment of air pollution and microbiological hazard for humans, in 45 public utility buildings in Cracow.

Material and Methods:
The study was carried out in four groups of buildings, including teaching facilities of the University of Agriculture and Jagiellonian University, churches, shopping malls and hospitals with outpatient clinics. Four sites located in the open air were chosen as control. The air sampling was carried out with MAS-100 impactor. Fungi were enumerated on Malt Extract Agar and the results were expressed as colony forming units (CFU) per m³ of air. The isolated fungi were identified by comparing macroscopic and microscopic observations with taxonomic monographs.

Results:
Mean concentration of airborne fungi was highest in the teaching facilities (1970 CFU/m³). These were also the sites where the largest range of fungal concentration was observed, i.e. from 0 to 23,300 CFU/m 3 . The lowest mean concentration (99 CFU/m³) including range was observed in hospitals (from 0 to 327 CFU/m³). Species identification of the fungal isolates revealed the presence of allergenic fungi (Alternaria and Cladosporium) in the examined spaces. Moreover, some strains were also identified as potentially toxigenic species, such as Penicillium expansum or Aspergillus niger.

Conclusions:
The concentration range of airborne fungi varied significantly between the tested spaces. Although the observed concentration of airborne fungi in the majority of buildings was quite low, detection of potentially toxigenic fungi indicates the need for monitoring of both concentration and composition of fungal aerosol in public utility buildings.