Background and purpose: Biological pollution in indoor air is mostly created through bacteria and fungi which are harmful to human health. In the present study we evaluated the fungal diversity of air and air-conditioning systems in different schools of Mazandaran University of Medical Sciences.

Materials and methods: The samples were collected from some rooms in different schools of Mazandaran University of Medical Sciences during spring and summer, 2014. The Quick Take 30 Pump-air sampler and carpet sterile fragments were applied for sampling of air and filter surfaces of air conditioners, respectively. The grown fungi were identified by routine mycological methods.

Results: Aspergillus was the most frequently species isolated from air samples (408 colonies, 28.26%) and surface samples (347 colonies, 24.89%). The highest fungal concentration level was reported from School of Medicine with Aspergillus (1152 CFU/m³). Among the Aspergillus species, A. niger (43.2%) and A. flavus (34.8%) were the most frequent species from the air and surface samples, respectively.

Conclusion: Both sampling methods showed that the School of Medicine had the highest level of fungal contamination over the study period. The high concentration levels of airborne fungi may increase the risk of respiratory diseases. Aspergillus which was commonly found in this study is one of the main mycotoxin producers in nature and is strongly associated with allergic respiratory disease, especially asthma.