Microbial contamination in buildings: comparison between seasons and ventilation systems.

Airborne microorganism contamination was investigated in naturally and mechanically ventilated buildings. Air was sampled with SAS system and cultured on general media for total count and on media for fungi; data were related to other indoor contaminants and to microclimatic parameters. Comparison of winter versus summer microorganism concentrations was not significant. No major difference of detected species was observed between naturally and mechanically ventilated buildings. In mechanically ventilated buildings significant correlations between microorganisms and relative humidity were found during the wintertime; a negative correlation between bacteria and particulate matter and a positive correlation between bacteria and temperature were found in summertime.