Objective: The aim of this study was to determine types and levels of airborne fungal spores in air-conditioned homes built after 1980without obvious moisture problems during the 2004 summer (rainy season) in central Florida, USA.

Methods: Eighteen single-family homes were selected based on protocol questionnaire and cursory inspection, which revealed no obvious moisture or visible fungal growth. Non-cultured spores were collected with Air-O-Cell cassettes. Three indoor air samples and 2 outdoor air samples were collected from each home. One indoor and 2 outdoor samples were not interpretable. Fifty-three indoor and 34 outdoor air samples were analyzed by optical microscopy.
Results: Several spore types were detected in the indoor samples, at levels generally lower than those detected in the outdoor samples.
Spores from the Penicillium/Aspergillus group were the most prevalent types indoors, exceeding the absolute levels and relative percentages of these spores outdoors. Ascospores and basidiospores were the most prevalent spore types outdoors. The percentages of other spore types (Cladosporium and Curvularia) were similar in the indoor and outdoor samples. Moisture-indicator fungi (Chaetomium, Stachybotrys,
and Ulocladium species) were nearly absent in both indoor and outdoor samples.

Conclusion: Airborne fungal spores are present in average central Florida homes without obvious moisture problems during the summer, at levels that are lower than those found outdoors. Spores from the Penicillium/Aspergillus group are prevalent in these homes, and moistureindicator fungi (Chaetomium, Stachybotrys, and Ulocladium species) are nearly absent. Despite climatic differences, airborne fungal spore types and levels in central Florida houses are similar to those found in other geographical locations.

Key words: Mold. Fungal spores. Background levels. Moisture problems.