Background and objective: Bioaerosols are airborne particles which can cause a wide range of health effects including hospital and occupational infections, acute toxic effects, allergies and cancer. Hence, the aim of this study was the qualitative and quantitative evaluation of bioaerosol in different wards of Malayer city’s hospitals.

Material and methods: Sampling was conducted from twelve wards in two hospitals. Both bacterial and fungal sample were taken based on method of ACGIH bioaerosol committee. The samples were transported to blood agar and sabouraud medium then cultivated immediately. The type and number of colonies were determined in the laboratory then, the bioaerosol concentration was calculated in terms of cfu/m3.

Results: Overall, the maximum concentration of bacterial (21.27 cfu/m3) and fungal (66.49 cfu/m3) colonies were found in pediatric and CCU wards, respectively. The minimum concentration of both bacterial (8.74 cfu/m3) and fungal (2.18 cfu/m3) colonies were found in autoclaving ward. Staphylococ negative coagulase(33.76%), Micrococ species(16.23%) and Bacillus  species(15.58%) were found to be the most  common  organisms and, Penicillium spp. (50.9%), Cladosporium spp. (27.02%) and Aspergillus spp. (8.1%) were the most common fungal genus.

Conclusion: Except of a few cases, total concentration of bioaerosols was lower than the guideline concentration (30 cfu/m3) in the all wards. High concentrations of bioaerosols in some wards can be explained by some reasons such as wear and tear of buildings, improper ventilation, incomplete disinfection of wards and, the high number of patients and visitors.