Outi Lindroos, M.Sc., Sanna Lappalainen, Phil.Lic., Kari Reijula, M.D, Ph.D. Uusimaa Regional Institute of Occupational Health, Indoor Air & Environment Program, Finnish Institute of Occupational Health, Helsinki, Finland, E-mail: Outi.Lindroos@occuphealth.fi

In this work we studied if accumulation of fungal spores to the ventilation channels has any significance as microbial source in indoor air. Concentrations of viable spores were determined from samples that were collected from ventilation channels, and the geometric mean and median values were calculated. The concentrations of fungal spores and actinomycetes on ventilation channel surfaces were low even in abundantly dusty channels, and therefore accumulation of spores in the channels did not seem to form any significant microbial source in indoor air. In the samples from exhaust channels in buildings with verified mold damages, prevalence of fungal species such as Acremonium sp., Aspergillus versicolor, Chaetomium sp., Eurotium herbariorum, Paecilomyces variotii, Phoma sp., Trichoderma viride and Ulocladium sp. was better indicator for damages than the concentrations of fungal spores.