The growth of fungi in air conditioning systems and buildings can cause certain diseases among which include asthma and allergic alveolitis. Environmental contamination by fungi inside buildings is primarily due to filamentous fungi and yeasts.
Many species of fungi can be distinguished, identified and classified according to their morphology, structure, mechanism of formation and spore-forming elements. Knowledge of these characteristics may be sufficient to identify species that belong to the filamentous fungi, but when it comes to identifying species belonging to the group of yeasts is essential to the application of biochemical tests.
General Concepts
Fungi can be unicellular or multicellular. Yeasts are unicellular fungi oval shaped (5-30 mm), stationary and dividing by various mechanisms, especially by budding.
Most fungi, however, are multicellular or filamentous and are characterized by being composed of branching filaments or hyphae that develop and intertwine to form the mycelium. There is a vegetative mycelium attached to the surface of the substrate (soil, plants, food) and an aerial mycelium or player, where they form spores (asexual and sexual).
Filamentous fungi and yeasts are mostly saprophytic, being free in nature, especially in decaying organic matter. Some species are parasitic, forming part of the normal flora of man, such as Candida albicans, a yeast and can behave as opportunistic and pathogenic result when a decrease in the resistance mechanisms of the individual. Other species of fungi can produce toxic substances during development or mycotoxins, eg aflatoxins produced by Aspergillus fla vus, which is a filamentous fungus. Moreover, some fungi are diphasic, ie, sometimes behave like other filamentous fungi and yeasts can behave like.
The conditions for a fungus to grow on a surface are: the existence of spores, nutrient base, humidity and temperature between 4 and 38 or C.
Most common species in indoor air
The most common species found in indoor air are shown in Table 1, from the results of two different studies (Health and Welfare, 1987, Flanigan et al. 1993) published in Indoor Environment Biocontaminants. The most common fungi in dust from existing domestic sources can easily become airborne, and if conditions are suitable for development in terms of temperature and relative humidity, can also be quartered in any material (such as carpets, wallpaper a wall, etc.). They grow excessively, throwing the environment a large number of spores with the consequent risk to health.
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