Airborne biological particles consist of viruses, bacteria, fungi, pollen, dander and other material of animal or plant origin, or their components or products. A number of respiratory health disorders are associated with the exposure to these particles, including allergic alveolitis and asthma. In many occupational settings, massive amounts of bioaerosols are released from the materials handled but in indoor environments, the exposure is rather characterized by unusual flora of the air and by toxins and other active products of the microbes. A major cause of biological contamination of indoor air is moisture accumulation in the building structures which creates ecological niches for environmental microbes with high biological potential, e.g., Streptomyces, Aspergillus, Stachybotrys, Trichoderma and Fusarium. Once these bacteria or fungi are growing on the materials of the building, their spores and metabolic products end up in the indoor air thus exposing the occupants.

• fungi and molds in buildings and their envelopes